I have frequently observed otherwise sober and rational online discussions dissolve into abusive arguments because comments that were meant to be conveyed with a light kidding smile were instead interpreted as rude, angry, or condescending. Sarcasm is notoriously difficult to get across online. Perhaps part of the problem is that online discussion boards tend to be so rough-and-tumble that people tend to read comments as attacks -- slaps as opposed to pats.
Until that changes -- and I see no reason why it will -- it may behoove us all to be a bit more blatant in our emoting. That may mean more exclamation points (please, no more than three at a time, and no more than one instance per paragraph), more emoticons, and more prefaces to comments. Especially when it comes to political discussion, emoting may be the difference between a healthy exchange and an all-out flame-war. After all, most of us political types tend to be snooty bastards!
To those who complain that more exclamation points and emoticons and explanations are hallmarks of bad writing, I say: you are absolutely correct. This isn't about good writing, this is about good communication. Good writing is (in many ways) objectively so, while good communication depends on an understanding of one's audience. In that vein, text messaging and informal emails simply should not be held to the same level as literature or journalism. There does not need to be poetry in that humble prose. Heck, I think it would be a huge achievement just to get people to spell things out rather than adopt the juvenile "C U L8R" style that always rankles me. I'll trade that for more exclamation points any day.