YouTube renders live stream comments as comments on a regular video.  Due to the nature of live streaming, people often post the same comment a few times in an attempt to have their comment seen and replied to by the host.  As you know posting the same comment twice causes the YouTube algorythim to flag it as spam.

Likewise eventually posting too many comments will cause you to be locked out.  Currently Live does not have a Capcha feature but hopefully it will.  If you get locked out of commenting simply click on your favorite HappyCabbie video (selfless promotion) and comment so you trigger the Capcha.  Then go back to the live stream and you can comment again.

Live still has some bugs and sadly it does appear to be on the back burner as YouTube is pushing Google Hangouts now.