Dave,
Well, the good news is that your question led me to the solution to the problem; it works now. I unmounted static-pages, then remounted it again, and everything is groovy.
The bad news is that I guess this means there is an undocumented (or, unclear perhaps) dependency on the mount ordering of static-pages and general-comments --- I had both installed and mounted, but I mounted static-pages first, which mucked things up.
The static-pages documentation says "You must have the General Comments package installed and mounted to use Static Pages"; maybe change "to use" to read "prior to mounting"?
Cheers, and thanks for the help!