I still don't know if it is systemically good for the author to be able to unilaterally hide comments from (nearly) everyone. In practice most people won't dig through [muted by author] comments and can easily be fooled by scammers, plagiarists, etc.
I prefer the downvoting model where it becomes a consensus, not unilateral, matter whether a comment gets hidden or not. Perhaps the author could get some extra temporary vote weight for this (considered paid for by the act of posting).
I very much question, particularly after HF21 with free downvotes, whether truly abusive comments won't get consensus downvoted by others. Already it mostly happens that way. The hidden comments are generally the truly garbage/abusive/disgusting ones.
Putting author-disapproved comments at the bottom of the sort order facilitates a variant of forum sliding where the author can (via sock puppet/collaborators) post many author-approved comments to push the author-disapproved ones so far down that no one ever sees them.
Some of these could also be used to help hide abusive rewards in the comments, too.