Perhaps revising "not voted on" to "has not voted nay or yea" would provide another perspective.

TBMOK, the voting options still appear after a "nada" vote, which makes nodes upon which a user has voted distinguishable from those where the user checked "nada." In fact, my perhaps mistaken understanding of the "nada" option is that it exists chiefly to allow correction of an unintended up or down vote on the consideration (because the action for "nada" is a nulop, IIRC).

If I'm correct (and that sometimes happens), then the request should be "possible." However, it would take quite a bit of dev work, but might drop the server load a bit.