I'm using Firefox 5 on OS X with Pentadactyl, a Vim-style keyboard navigation plugin (trying to reduce mouse as much as possible use due to RSI pain).
It's not possible to rate a page using the keyboard.
In addition, if you tab into the "I am highly knowledgeable about this topic (optional)" checkbox and select it, you can then not unselect it using the keyboard.
I have recorded a two-minute video showing the latter problem. It is here (sorry for the M4V/H.264 rather than Ogg):
http://dl.dropbox.com/u/10330141/articlefeedbacktool-keyboardproblems.m4v
Version: unspecified
Severity: normal
OS: Mac OS X 10.6
Platform: Macintosh
Whiteboard: wikimedia[unmaintained]