If you want to see an old version, you actually want to click on the "(no changelog)" anchor. Example: http://musicbrainz.org/release/997d975b-6092-4d2c-ab97-d8e25508750e/annotations
The anchor text really should be "view this version" or something along those lines. Especially given that the changelog on that page (example http://musicbrainz.org/release/997d975b-6092-4d2c-ab97-d8e25508750e/annotation/475396 ) always appears to be "Changelog: (no changelog)" no matter what changes were introduced.
(And the current anchor text is actually incorrect; the changelog itself is actually accessed by selecting a different Old and New, and clicking the compare versions button.)