3) The \mathrmsomething command does not make "something" upright, in my case. The problem is that the "mathrm" is encoded as mathvariant="normal" by htlatex, which should be fine, but then the "normal" is rendered as italic by pandoc. The workaround is to substitute "normal" with something upright, such as "sans-serif". So, between htlatex and pandoc, I run: