When I issue a
cat /proc/asound/version on my Core it shows version 1.0.23.
When I do it on the MD it shows 1.0.17
When I run alsamixer on both the Core and MD it says version 1.0.18
So 1.0.18 is the version of Alsamixer.
Your MD version is wrong. I don't know why. I would try to make changes to the audio and rebuild the image, and see if it grabs the right version. If that didn't work I would ssh into the moon unit and try and shoehorn 1.0.23 into it... that might not be smart advice. You might do ok with an upgrade on the moon, but if audio is all that is goofy, I would install the right version manually.
On the core where XX is the moon number:
chroot /usr/pluto/diskless/XX passwd
Change the password
New password, then I would do this:http://monespaceperso.org/blog-en/2010/05/02/upgrade-alsa-1-0-23-on-ubuntu-lucid-lynx-10-04/