It's not about individuals, and it's not about channels.

OP wants to be able to ignore any line that says things like:
mentors please invitation me join novice network
$/mil
2o%
c0m

Things that legitimate non-RMT players would never say.
Blacklists are ineffective due to size limits and RMT character creation rates, and channel filters are overkill. We don't want not to see a whole channel because of a spammer. We just want not to see the spammer. A spam phrase filter that automatically gags lines containing known RMT substrings would be a great feature.