Interesting, having dealt with my fair share of shit talkers / harassers over the years on Skial servers plus much more in the past with other games, it's not a new thing. You can't and won't stop it happening. policing this would be a nightmare and would become a she said he said thing, unless you can confirm through chat.
I do agree OP that some players ruin the fun for others with their behavior, that should be addressed as grieving, expand the grieving rule to some extent I suggest to cover players who obviously are on Skial servers only to harass, I have a player in mind right now that fits the bill that some admins are aware of.