The Ending [Reveled][Major Spoilers]

[Klarden]

Had another thought today: maybe the first part of the letter where he seems to do what he was asked is written BEFORE he steps away from the computer to see everything around disappearing? I mean like - he went through some tests and while feeling used still liked the idea of Unity. When he returned back (at least as it seemed at first) he starts remembering the events as Hive Mind speaks in his head. And this memories make him have doubts. And he starts writing the letter with doubts, but with the idea that it can be right. When he almost finishes something goes bad and he's getting a serious feeling, that everything's wrong. He starts looking around and everything starts disappearing. Than he understands SOMETHING (something i can't quite understand) which convinces him, that he's being used. So he writes the final part of the letter and sends it. That may explain the quick and drastic change of tone at the end of message.