Configure message editing and deletion

This feature is only available to organization owners and administrators.

There are several settings that control who can edit and delete messages and topics. By default, users have 10 minutes after posting a message to edit it, they can edit any topic at any time, and they cannot delete their messages.

Different organizations have different message editing needs, so this area is highly configurable. Two things are true under any configuration:

Message content can only ever be modified by the original author.
Any message can be deleted at any time by an organization administrator.

	Admins	Members
Edit your message content	[1]	[1]
Edit others' message content
Edit your message topics	[1]	[1]
Add topic to messages without a topic	[1]	[1]
Edit others' message topics	[1]	[2]
Move topics between streams	[3]	[3]
Delete your messages	✔	[4]
Delete others' messages	✔

[1] Controlled by Allow message editing.

[2] Controlled by Who can edit topic of any message.

[3] Controlled by Who can move messages between streams, in addition to other restrictions on editing topics.

[4] Controlled by Who can delete their own messages and Time limit for deleting messages.

There are a few useful things to understand about the message editing settings.

Allow message editing can be set to Never, Any time or Up to [a customizable time limit] after posting. If set to Never, users cannot edit message topics either. For any other value, users can edit message topics at any time.
If a user can edit a message, they can also "delete" it by removing all the message content. This is different from proper message deletion in two ways: the original content will still show up in message edit history, and will be included in exports. Deletion permanently (and irretrievably) removes the message from Zulip.