Board Thread:Support Requests - Getting Started/@comment-1447397-20140225064552/@comment-4845243-20140225074511

You're probably best off just deleting the inappropriate comments and blocking the offending users if they persist. Disabling editing for contributors is usually only done on specific wikis for reasons unrelated to your dilemma.

If you want, you could also disable comments and then use talk pages, which can be protected so that only registered users can edit them. That would be tedious though, and blocking the users would probably be less work.