Clarify m.room.redaction, remove duplicate entry

[aaronraimist]

Fixes #2171
Fixes #2172

As far as I can tell server admins cannot redact events in rooms where they don't have the proper power level so I have removed mention of that.

I have also removed

There is also a concept of a moderator hiding a message event, which can be undone, but cannot be applied to state events.

which doesn't seem to be a thing that exists.

[turt2live]

As far as I can tell server admins cannot redact events in rooms where they don't have the proper power level so I have removed mention of that.

This is because the implementation is limited and not the spec. The authorization rules permit it happening in both v1 and v3 (where the redaction algorithms are defined).

[turt2live]

"Users can redact their own events" is also misleading, as it can be prevented through power levels.

[aaronraimist]

Okay I think I have fixed that.

Is it a Synapse bug that if you set the power level for m.room.redaction to 0 that you still can't redact other user's messages as a PL 0?

[turt2live]

that's not a bug - you still need the redacts power level to redact other people's messages (over the client-server API).

[aaronraimist]

Oh I see. That's not confusing at all... I see how it provides flexibility on how you want the room to work but the difference between

"content": {
  "events": {
    "m.room.redaction": 0
  }
}

and

"content": {
  "redacts": 0
}

does not seem to be described anywhere unless I'm missing something.

[turt2live]

it's badly described, but it is described.

redacts controls whether or not you're able to redact other people's messages. Separately, but related, m.room.redaction under events determines whether or not you're able to send redaction events. An admin could block self-redaction by listing m.room.redaction events at a higher power level, and could confuse everyone by setting redacts at a low level but having m.room.redaction at a high level (you shouldn't do this). Moderators would require the permission to send m.room.redaction events (default events_default, default zero) and redacts.

[turt2live]

only one comment left - thanks :D This is looking really great.

[turt2live]

this still needs to keep the parts about users being able to self-redact. Would also be good to give context to "there" as the reader has likely forgotten by the time they read this.

[aaronraimist]

But I thought users may or may not be able to self-redact you mentioned a few days ago.

and yeah I can reword that. "may redact events there" is from the original sentence that's in the spec right now.

[turt2live]

A user's ability to be able to self-redact is controlled solely by the events object, not redacts.

[turt2live]

Thanks for working through this :D