I'm all ears.

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.

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.

Depends. I don't want to hear about all the things the ex did wrong. My first question when the ex blaming starts is "what was your part?" No one is an innocent victim in a bad relationship. If they can't acknowledge the responsibility in the breakup, they're not ready to enter into a new relationship. They'll just keep making the same mistakes again and again.

Definately not on first dates don't want to know about your x mkakes me wonder if you are compairing

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.