`File Usage' states: | Programs should be prepared to operate when `/usr' and `/etc' are | read-only file systems. Thus, if the program manages log files, | lock files, backup files, score files, or any other files which are | modified for internal purposes, these files should not be stored in | `/usr' or `/etc'.
On GNU `/usr' is a symbolic link to `/', if one obeys the above paragraph, then `/' must be prepared to operate as a read-only file-system (which would include localstatedir and sharedstatedir, which can never be read-only). It would be much clearer to write that exec_prefix, prefix, sysconfdir, and datarootdir should be prepared for read-only file systems.
