It seems that rebuild a wiki (
ikiwiki --rebuild) after changing the
underlaydir config option doesn't remove the pages coming from the previous underlaydir.
I've noticed this with the debian package version 3.20100102.3~bpo50+1.
Perhaps it is possible to improve this or mention it in the manual page?
--rebuild causes ikiwiki to throw away all its info about what it built before, so it will never clean up pages that have been removed, by any means. Suggest you do a --refresh, possibly followed by a --rebuild if that is really necessary. --Joey