The premise: When pinning certain messages to a channel, there are often changes that need to be made to a pinned message for whenever new information needs put in, or the rules change, or etc.
The suggestion: It would be very ideal if the mod or admin who created the message could toggle it edit-able by other mods, so that the burden of housekeeping wouldn't fall solely on one person, but on the entire moderator team.
An example: Admin creates a message that describes what each role is for. Admin pins the message. Admin toggles the message edit-able by her/his mods. 2 months later a new role is added to the server, but the admin forgot about the pinned message. Luckily one of the mods is attentive. Instead of bugging Admin to edit their message, the mod can do it herself very easily with this functionality.
Instead of saying (edited), the thing could say who edited it, for clarity's sake. Something like this: "May be important to have a mini "audit log" like the reaction log showing not only who edited it, but their timestamps too." - @NoDiscordHere