When a party declined his request to follow a specific format and submitted an alternate format he should never agreed to that alternate format. By agreeing to the alternate format he vitiated his original offer. Whether "that" address was in his previous offer is moot. "that" address becomes the agreed upon submission.
Exactly my line of thinking.
I believe that any submission where he specifically accepted or agreed, he would be liable for the terms, if this matter went to a court. He would additionally be liable for any arbitrary conditions placed in the "Optional comment" section of the submission.
The only problem is, courts could decline to judge a gentlemen's bet. However those who tried to hedge against pirate's default, and which Matt knew by his own admission, might claim damages by willfully leading them on. Who knows, maybe Matt tried to corner the debt market himself, which would lead this into outright fraud territority and liability.
IANAL