This dirty diff: https://en.wikipedia.org/w/index.php?title=Toyota_Land_Cruiser&oldid=prev&diff=720847140
As reported here: https://phabricator.wikimedia.org/T96701#4423989
AFAIK Parsoid should be able to round-trip embedded entities in html comments just fine (we have a special escaping mechanism we use), and even if we didn't, selser should be able to prevent a change to an unedited part of the article.
So maybe two bugs? Or maybe a VE bug which is defeating Parsoid's normal mechanisms?