I tried to highlight some code in this answer, by inserting an explicit
<!-- language-all: python -->
at the top of the file.
I also tried <!-- language: python --> just before the block of code, and have replaced python by py (as the latter is mentioned on meta-stackexchange) in both.
None of these seem to trigger highlighting of the python code. I am doing something wrong, but what is it?
The problem was python, which tells it to use the syntax highlighting associated with the tag python, which for some reason was set to "none". I changed it now, so both the methods you described will work. In the future, you can also directly specify a language from the list in that meta post (instead of specifying a tag), but you need to prefix it with lang, e.g. <!-- language: lang-py -->.
<!-- language: c# -->) more than closely reading the text and follow the links. And I know this had worked for me (but that was on Stack Overflow)