Do your comments show up after a few hours?

If so, then nothing's wrong, its just that the comment is still being read/waiting to be read by the Admins.

And for posts, it's the same thing, though it could also be that whoever posted the first comment on a post sends that post back to the back pages for some random, un-explainable reason. 

If it's something other than those reasons, then I have no idea.

Hope this helped!