I think it's pretty safe to say this didn't happen:

• Considering his love for privacy, I'm pretty sure nullius can keep his account secure so it didn't get hacked.
• If the account was sold, the buyer clearly is smart enough to earn Merit on his own, so he could have built his own account from scratch.
• Nullius didn't join any paid signature, which he could easily have done to monetize the account. Hacking or buying an account to make quality posts without earning from it would be dumb, and the person behind the account doesn't strike me as dumb.
• The pattern of posting a lot, then disappearing for a while, is consistent with nullius' post history.

TL;DR: nullius' account is not hacked nor sold.