Multi-Subscripts seem to exit KaTeX altogether

[DasNaCl]

This is a weird one. I'm trying to render f(e^A_i) = a_{1,i} e^B_1 + \cdots + a_{m,i} e^B_m, which works just fine on the katex.org web-widget.
If I embed this on my hugo-based site, however, things derail quickly. The equation is not rendered and no errors are shown.

It seems like whenever I use something along the lines of a_{42} KaTeX just does nothing, no error and no rendering. Purposefully adding an error here also doesn't emit an error, however, it does emit one when I remove the a_{42}....

Not sure how I even debug this, since no error is thrown. ☹️

[DasNaCl]

I see, escaping using f(e^A_i) = a\_{1,i} e^B_1 + \cdots + a\_{m,i} e^B_m makes it work.
It's interesting that I have to escape _ as soon as it pairs with {

Changing the processor from the someday to be deprecated backfriday to goldmark lets you use above expression without escaping.

[edemaine]

Yeah, I imagine it's a Markdown conflict of some sort. In particular _foo_ puts foo into italics, so multiple _s could cause problems in this way, unless you're using a Hugo KaTeX plugin which should properly parse and escape $...$.