That's not true -- I comment on HN but lurk everywhere else. The reason for this is, first, time commitment (I can really only be part of one online community at a time, although I do read other forums on occasion), and, second, I find discussions here more civil, comments more relevant, and emotions less charged than on other platforms.

In truth the polarizing of the Internet is causing a lot of us to be lurkers who may have things to say but do not want to engage in emotional content with strangers, because everything is interpreted so emotionally these days.