I guess if you report someone, you most probably don't want to see their content anymore. Kind of make sense.
NIP-65 allows to report a user with kind1984:
https://github.com/nostr-protocol/nips/blob/master/56.md
I reckon some clients use these reports to hide/mute/block some pubkeys reported by some your follows.
I guess if you report someone, you most probably don't want to see their content anymore. Kind of make sense.