XEP-0425: Message Moderation (in MUC) #20
Sometimes people post inappropriate content. XMPP has historically not had much more than IRC in terms of moderation tooling, ie kicking and banning, but today that might be considered insufficient.
XEP-0425: Message Moderation describes a protocol for a moderator to moderate individual messages, which would be nice to support.
Implementing enough of XEP-0425 to reflect when messages get removed by moderator might be a sensible first step. This allows moderation to be performed, either with specialized tools or other clients, as well as gathering experience which could feed back into getting the XEP moving forward.
Deleting a branch is permanent. Although the deleted branch may exist for a short time before cleaning up, in most cases it CANNOT be undone. Continue?