preserve  powerlevel
@@ -37,8 +37,15 @@ which should be preserved:
* `m.room.create` should allow the `room_version` key. Currently, redacting an
`m.room.create` event will make the room revert to a v1 room.
- * `m.room.power_levels` should allow the `notifications` key. Rationale:
- symmetry with the other `power_levels` settings. (Maybe? See
+ * `m.room.power_levels` should allow:
+
+ * the `invite` key. Rationale: this is required to authenticate
+ `m.room.member` events with the `invite` membership. Currently, redacting
+ a `power_levels` event will mean that such events cannot be authenticated,
+ potentially leading to a split-brain room.
+
+ * the `notifications` key. Rationale: symmetry with the other `power_levels`
+ settings. (Maybe? See
https://github.com/matrix-org/matrix-doc/issues/1601#issuecomment-511237744.)
