Although I'm disgusted by diaper fetishes, those people are merely expressing themselves through writing as well. This site is about freedom to be your real self and who are we (or anyone) to decide what quirks you can and cannot express? I say everything should be allowed, provided it is posted in an appropriate group.
Anyway, I believe that rewards for a positive contribution to the community are planned. (That was listed on the temporary homepage before the site really opened as a new feature.)