> I shouldn't offer it for sale as that would show the arbitration board that I don't need the domain. [...] So I could keep the domain but not use it for commerce...

If you're offering it for sale, you're clearly not using it for commerce. I'm sure if you finished you game and offered it for sale on that domain, you'd be fine. You're actually using it and in a non-infringing way.

So yes, if you're selling a domain and someone has a trademark for it, you should have to hand it over. Hell, I'd argue that should apply even without a trademark, but alas...