The later formula does not render because of the underscore(_) conflict. Markdown uses this underscore to italicize the phrase. Thus, mathjax is overridden.
I have this same problem. Hope the dev team solves this soon.
Yeah I actually figured it out shortly after posting. You can actually escape underscores in the mean time with the \ character, like in popular programming languages. I posted the workaround at the time in discord as well