It looks like the majority position -- which I would therefore suggest to standardize on – is that
- the Category name is the English name of that language, by itself: e.g. Category:French
- the home page for that language on the P2PF Wiki is e.g. French language with a preference for "Language" capitalized
yes, you are right, this was sloppy.
so yes, to standardize around single word category names,
and individual pages as you suggest as well, with 2 caps