How to find the user that edited a message?

Hi all - We have given our help desk team access to edit messages by adding the privilege suggested in . The users are able to edit messages after this and whenever someone edits a message, a small text saying the message has been edited appears at the bottom along with timestamp. However it doesn't say who edited this one?

I tried enabling audit policy as well for the 'Message' object under HR Help desk and ensured all attributes are selected. But the audit works only for few other attributes, but the actual message edit doesn't appear to be auditable. Has anyone managed to find the user that edited a message?