being muted is a disciplinary action concerning chat behavior. I see no reasons of boss battle deprivation since bad behavior does not in any way affect bosses. If its just additional punishment, i think mute status in a definite time is enough, otherwise it will lose its purpose.
Locked and removed. Not inline with the spirit of the game. If someone its not allowed to participate in parts of the game this can lead to perceived bullying and causes all kinds of issues. Additionally if you stop people participating, you might as well ban them. If the situation is dire enough for them to deserve being banned, they will be.