In reply to Bizarre spacing problem with Baskerville quotation marks:
Thanks everyone. I think it was a bug in the font itself. Someone from Linotype contacted me, and after re-downloading and re-installing, the problem seemed to be corrected.
I was just about ready to do what charles_e said and fix it in Glyph!
I appreciate the help — some of your tips will be useful for other situations in the future, too.