There aren't any posters that I really dislike. Obviously I have more in common with some people than others, sometimes this interest extends solely to one subject (football or sports for example.)
But I agree somewhat with Sofi. My favoritest posters are the "complete" posters, that can be funny, helpful and also great convo partners in a debate/discussion.
I also like it when there's a difference of opinion (not as in e-beef, though), with for example me liking one footy player and Bobbo or Thuggy not liking the same one and then we "talk it out". I've had some nice gun-control threads with Jokerman in the past, for example. Now at times I wanted to shoot him (huhuhu) for his opinions, but in the debate, in the difference of opinion, there's a link, a connection. I like that.
It's also got nothing to do with "being serious" on a messageboard, imo. It's still a message board, my jokes are just as serious as my WoW-posts for that matter.
I do have plenty of opportunity to discuss the more "serious" things in real life. And I do so, often enough. But apart from the interesting perk of hearing people from different countries on stuff, I'm always open to someone's view on "stuff".