Diffs for tag-only edit suggestions can be confusing

[cellio]

meta:291273

When a suggested edit changes the body of a post, the review shows the side-by-side diff, as expected. When a suggested edit changes only the tags, however, it shows the body once (nothing to diff), with the green background, and then shows the tags diff. This can lead reviewers to think something in the body changed (and spend time looking for it).

We do want the body to be visible for a review of tag-only changes (how else would you be able to evaluate the change?), but can we show the body with neither green nor pink background and add something like "no changes in body" to guide the reviewer?