I don't know what the solution is, but I definitely see the problem here. Though I question the efficacy of your solution.
Basically, I don't think that the solution can be a metric that can be so easily manipulated like that. As mentioned by someone else, a person could easily just upvote random content whenever they want. As well, it seems that it would negatively impact more casual users who aren't savvy with all the metrics, but are heavily involved in their network of people.
Basically, your idea puts on a little number that would harm many casual users while only creating a small hoop to jump through for some of the biggest contributors to this problem. That is, it wouldn't meaningfully effect their impact.
Perhaps tweaking your idea a bit so that rather than penalizing people for not interacting with more folks it rewards the folks that do.
Though personally, I can't think of any form of incentivization that wouldn't just cause people to adopt new steps in their output algorithms.
In fact, it seems to me that the more incentivization systems and complex algorithms we put in, the more we'll be alienating the mainstream rather than taking them in.
For people like me, who aren't super knowledgeable about tech stuff or blockchains or social media--the abundance of algorithms and whatnot can be a bit overwhelming.
Rather than adding on something new, perhaps there's a way to simplify something that already exists in a way that addresses this problem.
I don't know what that is, since I'm still learning the program. Maybe it's impossible. But that's my two cents.