Multi-user support: it’s something that Will wants to add, but it’s an open source project so it’s slower than what you might expect.

Deletions: it’s at best a “request to delete” with the Nostr protocol, not all relays will respect your deletion request. There’s no guarantees. Some people like it this way so that it’s more authentic. Damus won’t support deletions. Other clients might, but I haven’t seen any.