Actually, I think it depends. I am dating a man near my age. We both had long marriages. It would be pointless and too much work to try to pretend our ex-spouses didn't exist. A lot of mention of prior short-term dating experiences might make me react differently.

It strongly depends on how they are talking about it.
Sharing parts of personal life experience is pretty much fine. Comparing (even if positive) is not.

It depends on what / how is being said.

I'm all ears.

I try not to block any source of communication, as it may make it easier for the relationship to grow when you do not have to hold back the thoughts you are having. Hopefully, soon enough they will be thinking about you enough to never have the ex pass their mind

I don't mind it at all. My So has some serious hallrious stories sooo. Yep.. XD

I welcome it, especially early on. I watch what he says about the ex. If everything is her fault, that's a huge red flag.