4) Maybe a max of one rating per user per page?
(Perhaps later votes overwrite/overrule earlier votes? Or just discard later votes?)
This point is interesting and it's something I've been considering.
Right now I think the best route is to capture the vote and ignore it
later if required. I think an appropriate rating system will be
weighted (with respect to time) and take into account that wiki pages
change frequently. The purpose of gathering ratings for us is to draw
attention to pages that need improvement and to appropriately sort
similar articles in search results based on quality, since our wiki
can have multiple articles on similar topics.
It might also be interesting to have a weighted system to weight votes
based on how much a page has changed over time. So, when a vote of 3
is submitted and the page changes by so many characters, or so many
times, and a vote of 5 comes along, the resulting rating is higher
than (3+5) /2 = 4.