Long, broken MathJax expressions seem to break the formatting of all comments on a post, causing them to spill to far over to the right. In addition to making the comments hard to read, it can make the comments impossible to edit or delete, since the edit/delete buttons are pushed over past where the browser thinks the comment ends. This answer provides an example:
If I move my mouse over to "edit" or the "x", they disappear before I can click on them. This has been observed by at least one other user, who brought the issue to my attention.
In addition, a similar problem seems to happen with overly-long code blocks in mod messages, breaking all the messages in a conversation. Here is an admin-only link to an example; I'd appreciate it if the devs would check this out.