no, voting system will always get abused. There is never a perfect way to make voting system, people will find a flaw and abuse it.
Those who abuse the system would have their itch accounts banned & an IP ban put in place to deter them from making new ones. Itch already has a system for Two-Factor Authentication so make that a mandatory requirement when making a new account. Even the most ardent trolls will find it cumbersome to go through the entire 'make a new account' process alongside creating new 2FA info & verifying it every single time.
If itch wants to go further to prevent abuse, they could require phone verification with a valid phone number via SMS. That would significantly cut down on a lot of potential abuse. However, that would also exclude a lot of people so I feel the 2FA requirement becoming mandatory would be a nice middle-ground, even for those without phones.
Doesn't work, Steam has an even more annoying system and trolls as well as scammers go to the process. Newgrounds is not even inmunite to this either, trolls will make somewhere to 10 accounts, rise them up weekly and they would have something to affect voting. Not even Voat was able to come up with a better voting system, the best they can do is delay the abuse and try to find them.
Voting is always a bad idea.