Why does youtube give you a "comment pending approval" notification when you try to comment sometimes?

If I try to comment at some stupid video that has no real significance my comments always work no problem. If I post a comment on a controversial kind of video sometimes I'll run into issues. One is a "pending approval" message. These comments are almost never approved. Another issue is the comment deal just straight up will not work sometimes (always at a video with real world implications). Who's approval am I waiting for? The posting individual? Or some anonymous PC schmuck someplace? I tell you the more I feel censored, the more I feel like some rats are going to have to rooted out of our society. I know that will never happen though, so I'll just sit back and schmoe it up.