Flaming isn't anything that offends, or going off topic. Flaming is an attack. And it's not just the response to an attack, it's the very first attack. If someone stated an opinion, and I said, "You're such a moron!" that would be flaming. If I said, "I don't think you have the right idea about that," that's not flaming. If I said, "By the way, that reminds me of a movie I saw..." it's not flaming, even if it leads to more posts that are off topic. One might consider it rude (even if the person didn't intend to be rude) for someone to go off topic, but it's not flaming.

While PC has its own rules about staying on topic, in general, most boards accept that topics evolve, and don't require posts to be on the original topic. That said, I'm not saying there's anything wrong with PC having this rule; I see logic to both views. But going off topic isn't flaming. If the person doing so intends to stir trouble and get people upset, it's perhaps more than rude, depending how heated things get, but unless there are insults and personal attacks hurled, there's no flaming going on. In other words, flaming isn't the only negative thing that can happen on boards and email lists, and it's not a catch-all term for everything negative that happens in these groups.

A post may be "non-supportive," but it's only flaming if there's a personal attack in it. Non-supportiveness doesn't really have anything to do with it. Again, members may consider the post unsupportive, but that doesn't mean the post is negative. (Like my aforementioned example of being reminded of a movie, just mentioning a movie or saying something funny may have nothing to do with the original topic, but it's not an attack, either.) Even if it is negative, it doesn't mean it's a flame.

I'm editing this to add something I forgot: Danialla is right, in that not everyone will agree on what constitutes an attack. So, not everyone will necessarily agree on when a person is flaming.

I hope this helps.