I would say that based on the fact that MZ changed his PW after the forum's member's table was leaked, that MZ not only posted, but also traded/lent BTC a decent number of times after the forum was hacked would make it reasonable to say that his account was secured after the forum hack. In addition to this, MZ repaid a loan several months late, many months after the hack, communicated with shorena regarding repayment, and shorena did not mention anything about MZ's account getting hacked at the time.

I would also argue that the way MZ is behaving is consistent with how I believe the "real" MZ behaves. Although this can reasonably be faked.

Lastly, per theymos, the IP address of MZ is ~the same as what it was previously. If shorena can confirm some kind of proof of knowledge, then I would say that the person behind the MZ account is likely to be the "real" MZ.

With the above being said, I would still be hesitant to trust someone who has been away from the community for as long as MZ was away, at least at first.....