I'm also pretty sure that we have help pages discouraging the use from h1 to h4 because they render extremely here.
Yes, that's exactly why I made the consideration, Perl Monks Approved HTML tags discourages <h1> and <h2>, and it does disrupt the formatting significantly when used in the middle of a post/thread somewhere, especially on some mobile browsers, where the differences in font sizes are even more extreme. If it had been posted by a registered user, I would have /msg'd them first, but this was of course posted by Anonymous Monk, so there's no other option than consideration. (If I had the time, I might even look at the routines that filter the nodes' HTML, to see if those tags could be rejected automatically for AM posts. Or look at whether there might be some CSS changes possible to mitigate the effect.)