The most important thing to remember is that your comments should be related to the video. If you have something off-topic you want to say, start a new thread in the Conversation Forum or the Shenanigans Forum.
Here are some common reasons why your comments might have been deleted:
-the video itself was deleted (either for inappropriate content or because it didn't get enough votes to be promoted)
-your comment is not related to the video
-you are spamming to try and get a yack badge, or spamming in general
-you are flaming another user or you are being generally unpleasant
Also, if you post a comment in response to a comment that we are going to delete, we'll naturally have to delete your comment as well. So if you see a comment that you know is going to get deleted because it is breaking these rules, please don't bother to respond. You're just making more work for us!
The Cleaning Staff