A NIP to impose rate limits at the relay level for npubs posting the same message repeatedly. This should do away with most of it.

Mutes are just a list - why not tell clients to implement the ability to pull mutes fro additional lists that a user may pick, allowing a community approach to filtering on one side? On the other... I guess good implementations or methods to filter incomming posts; mainly thinking of strfry's Write...

Stats on what relays have the most and least of them could be useful to help pick relays.

Proof of work must be done.