Fact: I set all my videos to "allow comments with my approval only" - since I want to filter out any possible trolls. Hey, I show these to my friends and some of my co-workers too!
1.: When somebody comments, YouTube seems to silently "swallow" the new comment without proper notification to the commenter... so people keep "re-submitting" comments. I had several cases of repeat-comments now. I don't want to cause any drama by deleting duplicate entries because I'm sure YouTube notifies the author about the deletion. And as of yet, there have not been any troll comments, so I haven't deleted any comment except duplicate ones.
It would only take a tiny little bit of additional code to show a "thank you for your comment, it's pending approval" or some similar message.
EDIT: Apparently, YouTube says "Error posting comment, try again..." or some similar message. That is fail...
2.: I deleted a comment and the page didn't only remove the deleted one, but also the next in the list... I had to reload the page to see that it didn't actually remove it from the comments but only from my page. Now I'm worried I might accidently delete a regular comment.