If you see the following suggested edit (https://stackoverflow.com/review/suggested-edits/11026733), it will look like there is only one word change, and someone seeing is can quickly take the decision based on that, if they don't read the comment or go to the right side of the code blocks.
You will see the difference when you go to the right side of the code blocks.
I know, the reviewers should be careful to check all areas for editing. But I am not sure if all the reviewers do that. (For this edit, it's more likely that we will look for other edits, since we see only one word change. But when we have more visible changes, then the possibility is more to ignore the hidden changes).
So I think the system should somehow mark a codeblock if it has any edits so that anyone knows that there is an edit in the codeblock, even when no changes are visible at the first view.