It must have been deleted by a member of the team at some point and I think it's better not to add it back. The Greek sentence itself is not often heard. It would imply that someone is acting formally or is formally dressed. The phrases included in the incubator start with the pronoun "it" instead of "he". It's more natural to talk about "formal/official" stuff than "formal/official" people.
The only scenario I can imagine for this to mean "He's not formal!" is a comment made between guests at a "Black Tie" event about another guest turning up in a lounge suit and ordinary tie instead of a DJ (sorry you guys the other side of the pond; Tux) and Bow-tie. ;-)}
Yes, it could if it refers to an object that's masculine in Greek; for example, official results table = επίσημος πίνακας αποτελεσμάτων. But I think throughout the course the contributors have chosen to simplify things with masculine and feminine Greek pronouns translating only to he and she in English - I could be wrong.
I do think you meant επίσημη instead of διαθέσιμη in your comment (excuse my OCD, it can get annoying at times), but yes, you are right. ^.^ This word is hardly ever used as a noun. Only in certain, special cases, that one might never come across while learning Greek.
I'm not quite sure which alternative translation you are referring to here. An alternative translation is "He is not formal", which is correct, since επίσημος in Greek doesn't only refer to something/someone official, but also something/someone formal.
Επίσημο δείπνο - Formal dinner
Επίσημη ανακοίνωση - Official announcement
Is this the other answer you were referring to? ^.^
In a sentance such as this, is there any easy way to know that the αυτός here is an 'it' and not a 'he'? I get that here we sort of can tell by the adjective used, (although i could think of a context in which to say 'he is not official' in common parlance), but what if the adjective were vague?