If you select more than one revision in the History window where there is no difference (for example, a test that was self reverted), the main page display doesn't properly show that there is no difference between them.
Expected: A message by itself saying the selected revisions have no difference
Actual:
Another weird thing that happens with this bug is it takes quiet a long time to display the above screenshot (about 5 seconds for me). My total guess based off of no information whatsoever of why that is is because it's fetching the html of the webpage as a fallback or something similar.