I immediately scrutinize everything I do know about them because that is a bright red flag that they probably are not.

Could be worse, some people think that's enough interaction to tell you they love you.

I know a guy who would start every grossly exaggerated story with “to be completely honest”

Also remember the motto of that bumbling nitwit President W. Bush. Errrrrrr... You can fool all of the people all of the time, but you can't fool none of the people at no time at all. That's the logic he used in the Invasion of Iraq.

That the word "honest" even came up is suspect. Sounds too much like Trump.

There is the one way....stick around to give them opportunity to prove it

I would just ignore the comment.

Someone who does that is either terribly naive, or terribly inexperienced in the online world, or full of shit.

To be honest, they’re probably lying

If the word honest is followed by stable genius, I'd run

Seems like that is a staple of scammer vocabulary.

Honestly? You're honest?

"That's nice.".....blandly, of course.

I put my mistrust hat on.

Honest people don’t usually feel the need to advertise the fact. Without context it’s hard to really advise you how to respond.

"Aren't we all".

Riiiiiiiight

Ask them what internet provider they have there in Nigeria.

People who volunteer they are fair, smart, one of the "good guys", trustworthy, or honest, are none of those things. People who are those things don't have to point it out. I myself, for instance, am a stable genius. I know more than my generals.

Maybe they are honestly quiet?

I dont, because they aren't.

red flag.

Hahahaha . People who need to convince you that they are honest tend not to be

People who can be trusted don't demand to be trusted.

I get this same feeling when Trump or any other politician or sales man says any of the following;

"Trust me!" .... ummm why should I do that?
"I'll be honest!" .... Normally, you aren't honest?
"I won't lie." .... Normally you are lying?
"Truth be told." ... What were you telling before?

Do you have a reason to question their honesty? Do you give all people the benefit of the doubt until they prove otherwise? If you think all people are lying it doesn't matter what they say. If you give everyone the benefit of the doubt, then until they prove untrustworthy you can believe them. If you think about it, based on what people are saying here, if someone starts a sentence with, "To tell you the truth..." or "To be honest with you..." they must be lying. You don't have to respond to their claim at all or you could say "I hope you're honest" or "time will tell."