I recommend the Arcblock team to be as transparent as possible about this and state exact numbers of how much funds they collected, how much will be refunded and how much they will keep as a penalty. And then maybe consider just giving people these 20% back. It's just not okay to keep it if it's not needed for the project itself.
You sure you're alright mate?
Just because someone says there's specific guidelines to follow when making a transaction to invest, doesn't mean he can decide to keep 20% just because he says so. Because those "wrong" investments are not accepted right? Why would anyone keep that money then, if not for criminal intentions? Didn't they reach their goal with the sale already?
There's something to talk about if that 20% can be legally justified, but now it just seems like a percentage they made up.
The claim that too much gas/gwei/whatever will mess up their operation is ridiculous, why would it?