I frequently wish to copy short snippets or longer passages from web pages that include standard html text interspursed with mathematics, most often in latex rendered by MathJax, but occasionally in mathML. Is there any way to do this without having to separately hand cut out each instance of math and past it into the math editor? In other word, is there any way to get Writer to recognise embedded math and import it directly along with the html? Ideally, I would like math that is rendered latex to be imported as latex, so I could edit it; with MathML editing is such a pain that I don’t think that is so important (unless, of course, it could be converted to latex).

I will surely not be able to answer this question to your satisfaction, but I am interested in the field generally in the long run. To be able to shape my thoughts better, I would love to know some web pages giving good examples of the problem in your view. (You might edit your question and append some links / URL).

It would seem likely that Pandoc could handle this. It certainly manages HTML > ODT conversion, and you can see how the math options affect your use case.