Not a huge griefing problem but annoying nonetheless. Someone joined a channel I was in yesterday and started randomly starring and unstarring chat messages over and over. There was no way to stop them without a mod or channel owner so we just had to keep asking whomever was doing it to stop. After a few minutes they did, but it begs the question why there was no limit to what they were doing. I can only assume since they didn't hit the overall cap the system can't take any action (and you can't see who is doing it to report them).
I'd like to see some sort of short term rate limit on stars. Say 2 stars in a 30 second time period. And deleting the star doesn't reset the timer. Doesn't stop anyone from bulk starring, it just slows them down to where someone else can catch on.