A type of community policing could be enacted. League of Legends has done this with their Tribunal and it has had what most would argue is great success. This is my idea.

Through right-click (or social list) you can report someone for one of a few different types of Chat-abuse, this could include RMT tells/shout/yells, offensive language, or other like offences. If one character got enough reports in a particular time frame, say, 20 reports of RMT activity in 5 minutes, that character would get a 24-hour chat suspension automatically enacted by the system. Now, you ask what to keep them from just making another character and doing it again or what if someone is organizing the reports to troll someone else?

If you have a second character get chat suspended while your first is still in effect, the entire account is chat suspended for a minimum of 24 hours, or until it can be investigated.

If you are chat suspended wrongfully, you can voluntarily request a review where the last 10-20 minutes of your chat log can be posted to a system for volunteers to review and decide if it was warranted or not. If you are found innocent of any wrong doing, those that reported you wrongfully could be investigated for misconduct.