I was the moderator who handled the flags on the question. From what I can tell, he just needed a little bit of help to clarify that his question—while not great—is on-topic here. It didn't appear need a moderator to intervene at first blush.
When I looked at the flags, though, I saw:
too localized: Well, it's not too localized. While it might not be a problem every single programmer faces, how to design an RPN calculator is applicable to more than just a vanishingly small number of people.
off topic, belongs on Stack Overflow: the guy's not asking about a coding issue but how to design the problem, and if it is a crappy question, migrating it to Stack Overflow goes against the golden rule.
not a real question: this one had the most merit, but given a quick edit cleared things up, it really didn't warrant bringing a moderator's attention to it.
While I suspect that the user is trying to do homework1, based on seeing the question and evaluating the flags raised, I disagree that the question is so irredeemable that it required the swift hand of justice.
That said, it's likely to be closed by the community anyway in short order.
Note 1: I suspect there's a bit of an inherent bias at play when people suspect that someone is trying to get homework help, but homework questions shouldn't be discounted or treated any differently than other questions.