An ex (serious, many years ago) and I still have many of the same friends, though most contact is through FB now. If he has commented on a mutual friend's thread I don't add to that thread even if I have something relevant to say, feeling it might be a bit intrusive or something.
Is there some normal etiquette for this? Am I being over-cautious? He's never commented on a thread I've written on. I've always remained good friends with my other exes, so this hasn't come up before. This particular ex and I had a friendly break-up but things went a little downhill after and we haven't spoken in years, although there's no real reason why not. We've both moved on and I'd be happy to be in friendly contact, or at least be able to join the same conversations on-line!