This is part 1 of a two-part suggestion. Part 2 is here.
Many borderline or bad suggested edits are still getting approved. At the moment, there is no good way to educate users who make bad reviews*. Reviewers and editors are never notified if their decisions are disputed, or when an approved edit gets rolled back.
As one step to help that, the previous decisions of other reviewers, including custom reject messages, should be shown right next to the edit being reviewed.
This would help reviewers get an idea what other users think. It would also incentivize writing a custom reject message because there's a chance somebody will actually read it.
The argument can be made that this would influence reviewers unduly; that every review is supposed to stand on its own without any external input. However, the benefit of showing the other decisions outweighs the negatives:
Some clueless reviewers will think twice if they see reject votes from experienced users.
seeing a lot of approve votes on a bad edit may
aggravateinspire an experienced user to write a rejection message, helping educate new users.
also, it's not like Stack Overflow doesn't create plenty of bias when it comes to moderation decisions already - by showing downvotes and closevotes, for example.
This might be an easy change with great educational value.
* - One can post a comment underneath some SO contribution of the user to get their attention, but that is borderline stalking and should be used only in extreme cases. I also understand the team is firmly against any sort of punishment system for disagreeable reviews (like downvoting or flagging).