So I introduced the achievements, and obviously it takes less than 12 hours until people start abusing them. And even worse, failing in the attempt and then as king me to refund them. So here is a new rule. I do not punish past violations of this, but from now on, this will be in force:
Do not cheat to get achievements or to mine blocks. This includes client-side scripts, mods, transparency texture packs or any other way that gives you an advantage over the standard and intended game play. I know its hardly possible to check on those things, so claiming that you are using such is already worth being banned.