I'm not sure where on the Feedback Tracker terms and conditions, or dashboard, or anywhere else, that downvoting at will is prohibited. This is a non-issue that is receiving attention as an issue only because of an incredibly vocal minority. Upvoting certainly doesnt cause an outcry from users demanding written explanations for their upvotes, and serial upvoting happens just as often, where users upvote tickets that are of low quality so they might get a chance at attention or whatnot. I think that's equally bad or worse.
This ticket also begs the question: What is the function of upvotes and downvotes at all? It seems meaningless for a site focused on reporting and tracking user-generated feedback and bug reports. It's not a social media site or a forum. If I recall correctly, on the old Feedback Tracker, this functionality wasn't even possible.
One possible argument in favor of upvotes and downvotes might be, "well, it helps important issues get more visibility." For example, the Static Memory Issues ticket by @6wingseraph has over 200 upvotes at time of writing, and it certainly deserves attention. However, we have it from the BI staff themselves:
" ... ticket validity is not measured by upvotes and downvotes and will be processed regardless... " (https://report.bistudio.com/issues/FT-194?commentId=6ad4bff40a84f883660e1e21)
If this is true, then upvotes and downvotes truly have no bearing on how much attention a ticket receives. So, the "popular issues get more attention" argument goes out the window.
I see no reason for upvotes and downvotes to even exist. They add nothing to the site, and a user's Reputation score in terms of the upvotes and downvotes they've received has no bearing on the attention their tickets receive. All it does is add colorful banners to the user's profile if they receive certain numbers of upvotes. It seems this little bit of status is very important to some users.
I have been serially downvoted several times by several different users, who downvote close to my entire post history. It doesn't seem to matter or affect the attention my reported Issues receive. My profile has "gone into the negative" the same as @onno described above, yet my tickets still receive attention, comments, etc. It simply does not matter.