OK, I have been trying to get permalinks working without PATHINFO, for no other reason than that docs say it's possible. But in fact it seems not to be possible.
I even went so far as to export my wp database, drop it from mysql, install WP 2.6.1 from scratch, and re-import the database. At no point did permalinks work w/o PATHINFO.
And perhaps related, perhaps not, WP has no idea what theme I am using. It says the default theme is active, when it plainly isn't.
These things are pretty trivia in the grand scheme of things, but they make me wonder what else is wonky.