I've nailed a term for that "Whale votes farming".
I also think it's pretty bad for the platform.
The so called "weekly challenges" of many communities are oftentimes pretty boring and don't add anything valuable to the platform... Unless we're talking to the 2-3 persons ( almost always the same ) participating.
Sometimes I'm wondering if the engagement - comments - should be rewarded a percentage of the post value ordered by the number of like ( not the value) . That's how you create engagement.