Definitely agree! Also think hiding a comment should require entry of a reason, and should automatically notify the comment’s author of the action. Maybe also leave a “hidden comment under review” notice where it would normally appear in the obs (or other object), with a link to general information on why a comment might be hidden and what someone can do about it.
All of this in the name of transparency, to minimize chances for abuse of the feature. Abuse as measured against clear guidelines for when a curator should take this step, and when they should do something less drastic.
To answer @tiwane’s other questions, yes, I think hidden comments should be visible to curators, maybe via the “placeholder” link suggested above so they can still see what the screen looks like to non-curators.
And yes, I am OK with staff deleting clearly over-the-top comments, as they can already do for other content. Hopefully you will have some kind of internal tool for staff to easily see recently hidden comments and take appropriate action. And I would assume you would be permanently suspending authors of such content as part of that.
I agree with @cmcheatle also, that tools to more easily detect patterns of bad behavior would be helpful, at least to staff and maybe for curators too. But in conjunction with that, I think we need to seriously consider the related suggestions to re-think the curator system and keep the curator group from getting too big and diffuse.