I know that this probably going to be ignored, but I own a small text-only chan on the dark webs, and I was able to get rid of the CP spam overnight by:
Turning off auto-linkification of URLs.
Blacklisting all known URL-shorteners.
Blacklisting all non-latin unicode characters that are used to avoid word filters.
Blacklisting all unicode invisi-characters.
It's been over a month since the last time I was hit.