One of the editing guidelines for Wikipedia is "Assume good faith" (http://en.wikipedia.org/wiki/Wikipedia:Assume_good_faith). It strikes me that is precisely what "normal" people do not do when criticized but what analytical people tend to do, especially when communicating with one another (assume that criticism is not a personal attack or status seeking, but rather is taken at face value). In that vein I think your suggestions are useful and valuable for dealing with regular people in real life or people on the more vanilla internet c...
As someone who is often (as the article describes) willfully indifferent to the finer arts of conversation, I personally appreciate the directness and sharpness of discussion here. I feel like I can take people's comments at face value, and that I can usually assess a fair consensus about something by reading people's reactions to it, rather than having to figure out what social factors are influencing the posts. So I'm anti-politeness!
I do know, though, that a lack of grace in these areas can totally drive away some personalities, which is probably a mu...
I think politeness can be a range of possible values rather than a discrete quality. Being polite but also direct is fine, it's just when you start to edge down the spectrum of politeness towards being politic that it might detract from the quality of the dialogue. I do believe that one should still adhere to the rule of thumb: "Don't be a dick" even if one is being direct though.