This most commonly happens to 'random' people (those not involved in the heated debate) if they buy upvotes for their posts. Some very heavy whale accounts flag posts that buy upvotes under specific circumstances, such as Hive account@grumpycat who flags people buying upvotes on posts older than 3.5 days.

I think this in itself is good, as the only reason to buy upvotes that late is to secretly generate more income from your post. This is to the detriment of all other authors.