So how about spectating what looks like casual games on Vassal? I do point rules violations out in these situations. And missed triggers too. But only after they are really missed. (Something like, for next round remeber you have gunner o that ship). Is this bad form?
If you're a stranger, I would avoid that sort of behavior. Save it for after the match is over, not just after the round. That's what I would suggest.
Also, there's no guarantee that what you think is a casual match isn't really a league match of some sort, so you could be interfering with a game that has consequences for other players down the road.