It does not matter what system is envisioned there will be a way to game it.
No, that's repeated a lot in many contexts here but it is a wrong argument and I'm pretty sure @blocktrades would agree on this. You set up the system to reward the behavior you want and/or penalize the behavior you don't. Sometimes those can be cleanly separated and the end result is easy to predict, but even when they can't, you can understand the tradeoffs and still set up the rules accordingly.
Throwing up your hands in some fatalistic "no matter what we do it will be gamed" makes no sense when designing and implementing a system like this. The entire premise of all blockchains is based on setting up incentives for certain behavior and (in most cases) getting exactly that behavior.
The free downvotes are a pretty good example. They have worked out more or less exactly as predicted (which included things like retaliation and apathy). They're not perfect but also not getting gamed to any significant degree. The curve too for that matter. It has greatly reduced spam comment and votes. Getting rid of it will likely bring those back. Maybe worth it, but important to think about the consequences and what will be done about it.
Another counterexample would be adding a small direct cost (not just RC which is negligible at this point) to post. I'm quite certain that can't be gamed and wouldn't be gamed. It would simply kill most if not all spam (good) while also discouraging legitimate use (bad). So that's a tradeoff, but it isn't an issue of gaming at all.
Unrelated question :)
Does the HIVE sent to the DHF is being instant converted to HBD, or it is in a slow mode conversion 0.05% per day?
Instant