Additionally we have a moderator team that additionally looks for in-balanced behaviour.
I understand that a lot of people are asking on twitter for upvotes - so far we are able to filter those in the rankings. We are considering to communicate the policies even more public - but step by step.
Disclaimer: CTO @ PH.
Your assertion that "HN/Reddit are secretive" doesn't work for PH since PH puts a larger emphasis on real-life identity and impact. (HN has recently been more public with how it operates too.). Case in point, my parent post has 12 points. This is the perception of Product Hunt.
So far we have had the upper hand with ranking adjustment. But the fact that you believe it's mainly gamed - shows that we have to do a lot of work in improving our communication.
Maybe it was recent enough none of us noticed the impact...
Sorry i answer so loose/un-specific.
One of the advices of HN/reddit was to not communicate those things too openly in public. It's a bit against my nature but it makes sense from what i can tell so far.
Hopefully going forward it'll put an end to the impression that PH is easily and frequently gamed then. :)