(You can find the full list here)

Some people feel compelled to comment.  Some feel that they have humorous observations to add.  Others simply enjoy the self-referential nature of blog posts about commenting on blog posts.   Others enjoy the meta-story of how they comment on blog posts about commenting on blog posts. Sometimes, when the comments take a life of their own, the original blog post becomes irrelevant - it is only a host body to allow the comments to flourish.

Those that do not comment, and those that do, will have one thing in common.   What do you think that might be?