Notify user when a message mentioning them is significantly edited

Users should be notified when a message mentioning them (i.e. @everyone, role pings, username mentions, DMs, etc.) gets significantly edited. Example: I messaged my friend asking if they were still on to meetup with me the next day, and they said yes, but then edited the message to say they couldn't come because plans changed blah blah blah, and I had no idea until I looked at our DMs again.

Therefore, it would make sense to notify users when messages get significantly changed. Significantly in this case means the addition/removal/changing of more than say 33% of the characters in the message. Adding a check to make sure that the edit wasn't just spelling/grammar corrections would be necessary also.