As a >2k user on SO, I often review suggested edits.
If an edit formats code, I will accept.
If an edit changes code, I (along with everyone else) reject it.
In fact, I've yet to see an edit that changes anything in a code block other than white space that isn't invalid.
So, my feature-request is that:
<2k users be forbidden from suggesting edits that change code blocks (except whitespace)
Note that code formatting includes both addition and subtraction of whitespace.
At the very least, put a big banner in the review queue that says
WARNING: This edit changes code. There is a high probability it should be rejected as invalid.
I believe this minor change to the system would lessen the number of rejected edits - every rejected edit is an edit that wasted at least three users' time.
I would think it's obvious, but those users should be able to change code in their own posts (duh).