In a recent comment, one occurrence of stars-to-italics ('particular') doesn't render, but one does ('abstract').

This seems to be a bug. Is this the right place to report it?

EDIT: Per @MartinSleziak's investigations below, it seems to be something about the em-dash—like this. Hmm, it doesn't render in the post, so perhaps it's just a comment thing (as MartinSleziak helpfully indicated in the tags!).