Here's my take on it -- FWIW.
Of course, Comey's memo was "unclassified". It was unclassified because decided not to classify it; and he didn't show it to anyone else, who could have classified it, before he leaked it.
However, this isn't about the memo per se. It's about the contents of that memo, not the artifact called "the memo". Comey divulged the substance (he asserts) of private conversation with the President. By default, shouldn't one assume that all such conversations are "classified", unless deemed otherwise by the POTUS?
Comey should have checked, in advance, whether the President considered the substance of the conversation to be classified information. His failure to do so, does not make it right -- even if there isn't a classification stamp in the corner of the memo somewhere.
Has anybody asked Comey if there was nothing untoward in “leaking” this, why didn’t he just write an op-ed or let some reporter have it first-hand, instead of sneaking it through a friend who only gave the reporter a verbal accounting?
Classified is a small part of the issue.
See my post #25...(also post #17 is helpful)