If nothing else, I consider it a "common courtesy" to do minimal research into people (comment history, Google search) with whom I am communicating: it lets me get a feel for their level of language fluency, a sense of context for interpreting their values, and a better respect that the other person is actually a "person".

I personally believe that not doing this (either caused by not finding it important, or by an endemic challenge to the action by the communication medium), and not anonymity (as many people in the "use real names" debate claim) is what causes commenting community chaotic collapse (of the form of YouTube, 4chan, and random blogs).