Post History

This problem is now fixed, *but* you can't see the fix here because previews are turned off.  Previews are turned off because of [this problem](https://math.codidact.com/posts/287515) -- rendered Mathjax can be very tall and that did unfortunate things to the category page.  We're happy to turn previews back on if that's what folks want.  At least now they won't have the formatting error reported in this question.