I still do think there needs to be an opt-out. It's like I said before and the thing that keeps getting missed
Not allowing CC to optout while also having no restrictions on who gets to add, seems to say that you don't trust a CC to tag their work appropriately. Give them that trust, it will work for the site's benefit.
Also a thought - for the people that use gibberish tags, why not also have just a search opt out as well, as this is likely why people are using gibbersh tags in the first place. That way they can use the tags for their watcher's to filter without having to worry about the tag being used to find the art. some people are quite comfortable /not/ being searchable and would often prefer it.