I found some long-ago patches (not for this particular issue) from a
previous contributor (Daniel Espinosa), which surely worked at the time
they were written, but now break things. And Daniel stopped replying to
my mail. Sorry to be so vague, but memory is failing. If you want to
take a look, I can dig them up.
Karl, thanks very much for getting back to me! In the last two weeks as I've worked on Vala, I've already taken over Emacs's vala-mode, and I'm in the middle of trying to add ctags support to universal ctags, based on someone else's abandoned effort, so I'd be happy to have a look at Daniel's patches and see if I can salvage anything useful!