Since we are rejecting their edit, we should still be able to add a comment to the reject reason when reviewing a suggested edit as "Reject and Edit".
For example, take this suggested edit which attempted to add a
<!-- language --> comment to the post. He put the comment at the beginning of the post, which means the comment doesn't do anything at all (I tested, it didn't get used). The comment has to be placed directly above the code block it affects.
This means I had to go in and improve the edit just to move it to a different spot. I chose "Reject and Edit" instead of "Improve Edit" because it wasn't helpful. The edit he made was incorrect since it was in the wrong spot. But that suggested edit permalink page only marks it as "Rejected by Community ♦" with the canned reason that the edit didn't correct critical issues with the post. It would be nice to be able to explain to the user that they put the comment in the wrong spot, and how to properly insert language comments. Also, the canned comment wasn't really correct in this case.
Note: I know some people might argue that I should have instead chosen "Improve Edit" since it made me make the correct edit or whatever, but that is a bad argument. You have to remember that choosing that option adds that incorrect revision to the revision history. It's far better off only having the correct revision. Also, the suggester will likely just ignore it, and make incorrect edits of the same type later on.
Also, expanding off a previous suggestion I made, the reject reason should be listed under my username rather than Community, listing Community as a second reject-user only when another user hasn't rejected the post as well.