Currently, the following happens:
- Page is marked for translation
- Vandalism is added to page
- Vandalism is reverted
- Page still shows up in Special:PageTranslation as having pending changes and must be marked for translation again.
When the combined "changes" diff is empty, it is a waste of time to mark the page for translation again. At very least pages with empty "changes" diffs should be hidden from Special:PageTranslation.