I don't actually know if this is incorrect behavior, but it strikes me as
funny:

term% ramfs -m /n/ram1
term% ramfs -m /n/ram2
term% bind /n/ram1 /n/ram
term% bind -a /n/ram2 /n/ram
term% mkdir /n/ram1/test
term% mkdir /n/ram2/test
term% touch /n/ram1/test/foo
term% touch /n/ram2/test/bar
term% ls -l /n/ram
d-rwxrwxr-x M 47 nwf nwf 0 Jan 27 23:55 /n/ram/test
d-rwxrwxr-x M 45 nwf nwf 0 Jan 27 23:55 /n/ram/test
term% ls -l /n/ram/test
--rw-rw-r-- M 45 nwf nwf 0 Jan 27 23:55 /n/ram/test/foo
term% cat /n/ram/test/bar
cat: can't open /n/ram/test/bar: '/n/ram/test/bar' does not exist

Why don't I see /n/ram/test/bar?

Kernel sources are relatively recent (replica/pull done a few days ago) but
the same behavior happens in 9vx, which makes me think it's deliberate...
but the existence of /rc/bin/replica and /386/bin/replica both suggests to
me that these are supposed to be unioned together to allow replica/... to
work at a command prompt?

--nwf;