I'm a bit of a contrarian, so I'll point out that you need a little conflict and negativity in any group/relationship, or it remains superficial and stultifies. Obviously it's a matter of degree, and most segments of the internet have too much negativity, personal attack, trolling, etc.
But forums can make the opposite mistake, too, and insist on too much niceness and harmony, screening out anything that might possibly lead to conflict or unpleasantness. You need to allow for some of that, or else things remain superficial and inauthentic, not to mention boring. Same thing in any relationship or group.
I heard some stats on it from Jordan Peterson (who does not exactly shy away from conflict, lol), saying that if the ratio of negative to positive drops below 1:10, the relationship is in trouble. That's from Gottman's research, the guy who is well known for intensive studies on marriage success/failure. Gottman's research suggests you need 5 positive interactions to balance out every negative one; that's pretty well known. This other stat is less well known, but to me it's more interesting. If the ratio drops below 1:10 (in other words, if there are very few negative interactions), then that also predicts marital failure.
I'm extrapolating from marriages to forums, and that's admittedly a stretch, but there's a point in there about things being too positive, nice, pleasant, conflict-avoidant, etc.