Yeah, the up/down system is what prompted lots of bots to get created in the first place. because it leads to super easy post manipulation.
Get rid of it and go back to how web forums used to be. No upvotes, No downvotes, no stickers, no coins, no awards. Just the content of your post and nothing more. So people have to actually think and reply, rather than joining the mindless mob and feeling like they did something.
you do realize that ads appear in more places than just youtube, right?