If I rate a modification and then reload the page, the ratings, as well as the rating score increases..
Since only the first time you can actually rate the mod, if you rate a mod with 5 points, on each reload the mod will take an extra 5 point rating.
To reproduce:

Rate a mod (suppose it has a score of 5 and one rating)
Rate it with 5
Notice that it now has a score of 5 and two ratings
Reload the page
Notice that it now has a score of 5 and three ratings
You can go on all day doing this..lol
This for a 0 rated mod will have a good result, but if we suppose that you hate a mod author,you could enter 1 as a rating the first time and keep reloading the page until the mod' s rating goes ...eight below :lol:
This happens also rating as a guest..