I think the very premise of this "Roundtable" is flawed: Given the propensity for humans in large and relatively anonymous groups to descend into fatuous vitriol and misspelled narcissism, why bother at all?

This isn't the case. Sites like Lamebook show us that people will attach their face and names to stupid things. There are countless (semi-) anonymous webforums, etc that provide useful discussion. You are right, it doesn't matter what type of community you post in.