pointing out mistakes.

On occasions, when your opponent has missed an opportunity, do players ever point this out to them, or is this frowned on in chess etiquette? What about offering unsolicited comments after the game has finished?

I only ask because I am very ignorant fo etiquette, and recently there have been a few occasions where my opponents missed opportunities, and I felt a strong desire to point it out. The excuse being, of course, that such advice might help them improve their game, but to be honest, upon deep introspection I realised that any desire to help fellow players was the lesser part of the motive, the greater part being a desire, not to gloat, but more to express my relief at having escaped a forced mate, loss of a rook etc.

So to summarise this long rambling post, my question is, is it ever okay to comment on your opponent's play or moves, and if so, in what cirumstances (and what kind of comments)?

Context is the deciding factor.

If you're playing a like-minded friend then pretty much anything is okay. A tournament game against a stranger? best to keep it to yourself.

Most players will ask for advice if they want it, this usually happens when they know they have been soundly beaten by a considerably better player. No advice should be given after games in which your opponent has blundered a good position, that's just a little too rich.

I dunno, sometimes I'll say something like: I was really worried you were going to play 25 d5, or something like that. It never occured to me someone could be offended by that...

This has to be pre-agreed or there must be some sort of mentor/coach - student dynamic here ... or else it easily appears rude, however well meaning your intentions are.

Even if you're dying to point something out, wait until the game is over and EVEN  THEN -> Ask if he's okay going over the game with you.  

This game bruises egos rather easily and most people would rather live in denial than be constantly reminded that they didn't see stuff.

Of course, on the flip side, I annoy the heck out of a strong player in post-mortem and I try to get a free lesson out of it.

That's more of a compliment rather than pointing out errors now, isn't it? The OP alluded to pointing out "missed opportunities" ... people tend to get touchier about stuff like that.

I, for one, would not be offended.  I can't think of anytime that anyone at chess.com has offered me advice during/after a game, though.

I've offered advice and I've never had anyone act like they were offended.  There have been a few people who didn't reply, so it's possible they were offended and just didn't tell me. 

I hadn't thought about people being offended, though, and I may be less likely to offer advice now that I think about it.

After I lose? I don't need my opponent's advice or reassurance. Proper etiquette, I believe, would be a handshake, or "gg". Obviously, if someone directly asks for your advice or reassurance, fine. If they give it without you asking, they pretty much suck.

I used to get a friend extremly angry by doing this.

"Snatch not eagerly at every advantage offered by his unskillfulness or inattention, but point out to him kindly that by such a move he places or leaves a Piece en prise unsupported, that by another he will put his King into a dangerous situation, etc." - Ben Franklin

I kind of agree with other parts of his essay like don't tap your fingers...no celelebrating...no trash talking. This suggestion is a little odd.

Ironically, if he would have started saying that stuff to me, I would have tasered him

 I think Ben was just trying to work the word "snatch" into the conversation.

Yes, they tried to help you improve.  They must be horrible nasty people.

Just because it's free, it doesn't mean I need it, Bald...r

Actually, trysts, you can be a little abrasive sometimes. Just saying. 

Thanks for the useful advice.

most of th times i pointout the chances i missed and the mistakes i made too. overall we are playing for fun. nothing wrong in pointing our mistakes and informing their winning chances. But whatever we do, we should not insult or make others feel bad about their mistakes.

useful thoughts