Immoral if there's a kid because then he/she is screwed for life. Moral if they are consenting adults with no consequence.

Unless the couple are twins; one will be older than the other, there are issues with consent, age (being a minor), and perhaps specific circumstances could make it acceptable, but not "moral".

just will not have sex with my daughter

It isn't something I would do and I think it's icky but, so long as those participating don't have children, I don't care in the slightest.

non sequitur , the question is too vague to be answered definitively one way or the other. An incestuous relationship between legally consenting parties is none of my business provided that intercourse does not result in the birth of a child. There is no sensible reason to subject a child to that kind of genetic predisposition to defect and social scorn. Otherwise, I couldn't give a toss.

I don't know if I would say that it was moral as much as i don't think its inherently immoral. Of course that statement has to be qualified. I think if both parties are consenting adults, and that assumes that there is no coercion, then I can see anything objectively wrong with it.

I am saying immoral just based on criminal statutes. There are also issues of genetic disorders from incest.

I can't say moral or immoral because those are social judgments based largely on social norms, but also on facts, such as inbreeding. But the truth is that pederaste was common and accepted for generations in Europe, royalty and aristocracies have in-bred publicly and even today, supposedly "moral" religious practices (not just LDS cults) marry off their children at young ages even to close relatives. I'm not sure how society has come to look down on what we call incest, but I'm sure that had a lot to do with the advent of rights-recall that even in early America, women and children were chattel and could be beaten by the male owner... until society started changing the narratives and fighting not only for women's rights, but also for the rights of children to not be abused... and our social definitions of child abuse have also changed consistently and incessantly for eternity.
As a product of a western society upbringing, I still have thoughts about incest being abuse, but, a better question is to ask the theist to justify all the incest, pederaste, and the forcing of victims to marry the rapist...Which is more "immoral?"

The offspring will be freaky mutant kids.

Bad genetics

For me incest is immoral, but what others do is not my concern

Nasty!

If it's consensual and safe I could care less.

There's a book (and movie), by John Irving, called Hotel New Hampshire about this subject. Both were tastefully done because Irving is a great writer. I recommend them.
I think it's a common fantasy because sex is really about power and siblings want power over siblings, children want power over parents, and younger brothers/sisters of parents are seen as mentors (which is a cool idea concerning the biggest issue facing 18-25 year old humans). I don't think it's a good practice in reality but of individual case and hard to predict. I do think siblings, especially if one is a male, can benefit from being much less private about their bodies and teaching each other. I see absolutely no issue between same-sex siblings over 16. In fact, it might help.
The problem with porn is that it can normalize certain ideas and this is a big fantasy for many. I do think it's a subject which needs to be discussed more often, and openly, in appropriate forums so that we can explore the roots of causation. In general I think humans treat sex as an icky, or nasty, thing but it should not be that way. If we were more open and communicative about it I think there would be far less harassment and rape.

even without the possibility of deformed progeny, this is also a psychological and social minefield - incestuous partners would be obliged to hide their relationship and may suffer from doubts and guilt about being 'wicked ' or 'sinful' leading to isolation, rejection and countless other mental issues.

Biologically everybody wants to experience the pleasure of sex as soon as they find their "tickle zone". Babies get erections and rub their pelvis on toys, but that doesn't mean you poke them with a vibrator! Even animals wait until their young are of age! Incest, whether of age or under, is only practiced in the animal kingdom when the herd is too small, or other options are limited.
And this brings me to instant gratification versus waiting for the right time. It's easy to form a bond with a sibling in this day and age of multimedia and staying home for safety. More time home equates to Idle Hands (devil's playground). Instead of waiting for somebody right, you use each other for pure gratification. Later on, she'll get married, or he'll find "the one", and that sibling bond will be missing because you cannot look each other in the eyes, out of shame of yourself, not the other.
There are many types of "love". The love for your mother is not the love you feel for your pet. The love of ice-cream cannot be mistaken for the love of your life. Sibling love should not be sexual love, morally, logically and pretty much biologically.

In theory, incest wouldn't be immoral. But the way our culture works, brothers and sisters, children and parents do not have sexual relations. For this reason, there is too much emotional baggage and damage potential. I would not condone a sibling relationship, because it is fraught with potential for serious problems.

If I met someone who told me they were INVOLVED in such a relationship, depending on the details, I wouldn't feel the need to end the friendship or lecture them. I could accept it in some circumstances, I think. But relationships are hard enough without adding cultural baggage and emotional damage.

It is immoral as long as either one is not an adult with the intellectual ability and knowledge to understand their actions. They must not have had psychological or physical incestuous relations in their youth with each other or others. There should not be any history of incest or pedophile relation with any other adult prior to their relations. I do not believe they should be sibling or parent child relations. If they have incestuous feelings that are troubling they should seek counseling.

Just because one does not believe in a God does not mean one can be a sexual anarchist.

Neither was not an option. Incest is not good from the gene pool standpoint but neither moral or immoral if consensual.

Too many variables to consider. As to your question... it's not really, it's procreation between parent+offspring, uncle/aunt+niece/nephew, siblings, and half-siblings that is just not right. Based on genetics, the risk of having a child with your half-aunt/uncle or first cousin doubles the risk of having a child with a birth defect... which brings it up from 4% to a whopping 8%... which honestly isn't that scary.

There are studies that find some minds are wired (genetics) to be attracted or repulsed by the thought of doing the deed with family. Sex between two consenting adults has always been and always will be alright in my book. I've personally been attracted to a cousin and a half cousin, both of which I was not raised with having contact prior to puberty, have had absolutely no sexual contact with. It's like being young when your mom remarries and you grow up with your step sibling vs your mom remarrying when you're in your late teens and your new dad has a daughter that's cute and around your age, with the former you're more likely to be grossed out by the thought while with the latter it's far more likely to be attracted. It's attraction, it can't be stopped, only controlled.

I've not been involved in any type of incestuous activity, but I know a guy who married his first cousin without knowing it was his first cousin until about a year after the ceremony (estranged family and all that). To the best of my knowledge they're still together and happy, had two perfectly healthy baby boys. It happens, may not be your cup of tea, but as I stated, there are too many variables to consider before labeling it moral or immoral.

Personally I find sex between two consenting adults (with intact healthy minds, i.e. no retardation, disability, etc.) has always been and will always be okay in my book.

I actually don't see it as a huge deal if cousins or distant cousins decide on having some sort of relationship or even children. The genetics would be way more diverse and you wouldn't be raised in the same household so it's not the same as siblings.

Now siblings is immoral for many reasons. Your children would face repercussions of not having enough diversity in their genetics one way or another. If the siblings decided on just a sexual relationship then there is A LOT of emotional problems that could and will occur if it happened and shame since it's a very taboo thing and could ruin your relationship with them as a whole.

Moral it was a social norms until like the last 100 years and so long as no genetically flawed human is born who cares

If we accept that individuals decide what they want to do with their bodies then that is all we should say. They decide how they want to live their lives. There are 7 billion people on earth. Why should what 2 of them do matter to anyone.

Just to be clear I don't personally like incest. I just don't see my sibling in that way. But for everyone else, who am I to judge. We only get 1 life, so that means no one is an expert at living and we cannot tell each other how to live. At least that's how logic works.

I think it's more of an issue of how it might affect the dynamics of your family WHEN discovered. Also, it's kind of like when people date at work, break up, and how it affects not only their work but their co-workers sometimes. Just not a very wise relationship move. Moral vs Immoral - that's a tougher call. I guess there are personal morals and community morals - and sometimes it's not easy to separate the two, unless you live in an isolated situation. Rarely a wise choice - I'd say, and frowned upon by most, for sure - I'd just steer clear. I'm sure there are exceptions (I sometimes wondered about Angelina Jolie and her brother). We all might say "who am I to judge" - and then we do, we do judge. So, again, not a winning move.