Yeah, I agree this would be bad. I talk a bit about this here: https://ericneyman.wordpress.com/2019/09/15/incentives-in-the-election-charity-platform/
A possible solution is to send only half of any matched money to charity. Then, from an apolitical altruist’s perspective, donating $100 to the platform would cause at most $100 extra to go to charity, and less if their money doesn’t end up matched. (On the other hand, this still leaves the problem of s slightly political altruist, who cares somewhat about politics but more about charity; I don’t know how to solve this problem.)
And yeah, we’ve run into Repledge++ and are trying a small informal trial with it right now!