For now, people react like "You're an asshole, I'll just kick you and keep on with my rude comments" because they can go away with it. IF you could end in a deadlock, they wouldn't have much options :
- They keep bitching on each other and just waste their time. If no one manage to calm down, you could just leave, because it would always be better to wait before a new duty that may be fun than going on with a toxic duty.
- They realize that this will go nowhere and decide to be smart enough to stop wasting their own time.
So, in fact, allowing a deadlock can push people to stop being idiots instead of giving them the right to do so without any repercussion.
To go back on the GM part, they can't do much for now because the rules of kicking are a blurry mess. If you can call a GM because someone is purposely screwing the duty, during the duty, it will solve the problem far quicker. And if people "leave the duty" or "log out" in fear of the report, then you're not 4 anymore and you can have your majority. Besides, the fact that people can be reported for that
with real consequences, is often enough to calm people down.
Oh, and I'd also put an automatic withdraw if the party is out of combat for 10 minutes.