There is a delete event but not sure which relays implement it, so results might be interesting. Possibly you end up with the event on some relays but not others. Also even relays that do remove would need to keep a record of the event id else it might end up being rebroadcast and turn up again..!
Discussion
And clients (more-speech for example) may not delete a message once recieved from a relay.
>From: squaaalal at 07/17/22 03:54:18 on wss://nostr-pub.wellorder.net
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>There is a delete event but not sure which relays implement it, so results might be interesting. Possibly you end up with the event on some relays but not others. Also even relays that do remove would need to keep a record of the event id else it might end up being rebroadcast and turn up again..!