The text above describes new event kinds for public chat channels and client-side moderation in the Nostrum Improvement Proposal (NIP) 28. It reserves five event kinds for immediate use, including creating a channel, hiding messages, muting users, and basic metadata. The new event kind 44 is added to mute a user in a channel. This event is similar to kind 42 replaceable events, where the information is used to update the metadata without modifying the event id for the channel. Only the most recent kind 44 is needed to be stored. Clients should ignore kind 44s from pubkeys other than the kind 40 pubkey. Clients should support basic metadata fields: name, about, picture. Clients may add additional metadata fields. Clients should use NIP-10 marked "e" tags to recommend a relay.

Link: https://github.com/nostr-protocol/nips/blob/master/28.md