It's too much effort for it all to be a joke, as for the spelling mistakes, disorder, and grammatical errors, it really doesn't matter according to the way they got the achievements.
See, what happens is that the gametuts people have a special version of xbox live that is only allowed to the game developers so that the games can be tested in action and what not. So what the gametuts people did was acquired such things and then sent a false information by hacking the xbox with the account, this allowed the account to unlock the achievements under false pretenses in a random manner that all the achievements were unlocked at the same moment.
This is why the list is the way it is. The disorder is due to the random unlocking and the spelling mistakes are because the developers simply made the achievements and didn't have time to make corrections because its a prototype testing xbox live version.
The achievements were right at the time, but bungie has the ability to go back and edit, create, or delete achievements. So these might not be the final ones when the game comes out.
[Edited on 07.15.2009 10:27 PM PDT]