When I post in forums, I use variety of styles. My favorite is humor. I am active in an on line bipolar support group and find that making people laugh can help people deal with a depressive episode.
But, I can be serious as well. I was involved in one series of posts that sought to steer the direction of the group away from what I felt to be a series of personal attacks on other group members. I was moderately successful, as we reached a compromise that I believe all group members can live with.