It might be interesting for folks to look at John Suler's writing
Interesting, thanks. I have skimmed it, and there are more articles that worth reading. It is an interesting topic.

Suler starts with what we all observe (that folks tend to act differently IRL than OL) and tries to pick apart the threads that lead us there. In general, all effective communication is built on a combination of unconscious rules and social cues, or signals from those we're interacting with. If I know that the lovely and loquacious denuseri believes she should not speak first, then I know that I must. If I say something and her face twitches, I know that I've hit a nerve and need to proceed with extra care.

The ability to do those two things (grasp the rules, grasp the cues) is so central to our functioning, that we recognize those who lack them as possessing a form of mental disorder (in this case, to a greater or lesser degree, Asperger Syndrome).

The point that Suler makes is that exchanges OL mess with our understanding of the rules and deprive us of many of the cues we'd naturally receive in face-to-face exchanges.
Many have commenting on that, calling this 'the flat media'. We are aware that we are missing clues that we rely on in RL - I believe some researchers claim that 90% of our communication is mimic and body language. That is why 'mimic' is added on - :-))

I think one should not underestimate the mix of cultural norms either, which even in f2f communication often cause problems until get to know each other better. I have a feeling that this is less clear to people in general, at least it is not much discussed.

We tend to press ahead too vigorously, say too much, demand too much, misunderstand too much, recoil too much. In effect, we accelerate the development (and decay) of our relationships. IRL, even at a gathering of like-minded souls, there's better social enforcement of norms and richer symbolic environments. In consequence, we're able to play nice.
This may be too much of a generalization. Many people hold back, express themselves carefully, or are content with reading alone.

It may also be an idea to take into consideration that a great many topics are discussed which are quite sensitive, while RL conversation is perhaps less so much of the time.

It is also not true that there are no rules. IME very few lists have no rules, and they are sought upheld. The rules are basically the same all over, play nice, go after the topic not the person, sober language.

But truly some people can be consistently viscous online, to a quite hair raising extent. The only explanation I can find for that is that they use other (unknown) people as scratching posts for their own inner frustrations - anonymously. The phenomena is known and warned against.

But if you are getting to know a list or whatever and some people on it, I believe that many of that same rules from RL will come into play. I do not think we all see others as just disembodied ghosts floating into space, rather it can be seen as a mind to mind contact where you get to know people and appreciate them, even make friends or fall in love. A surprising number of people move countries because they fell in love over the net - a dangerous place ;-))