[jiveturkey]

It's not unprofessional at all. It's the standard. Nobody on the receiving end likes it, and many on the hiring end don't like it either, but it is what it is. For a company the size I imagine The Atlantic is, you're lucky to have even gotten a no from the recruiter. Many companies just drop you without further contact. (That is a bit unprofessional.)

Sounds like this may have been your first job interview ever, TBH.

Move on.

At your next interview, ask the final tech interviewer before you leave, what their impression is. I wouldn't do this with every interviewer because the response (good or bad) will change your psyche and affect the rest of the interviews through the day.

Don't bother asking the HR person (usually they are the final person you speak to before you leave), they won't tell you anything useful. For smaller companies, where the HR rep will have some useful feedback for the hiring manager, do make an impression on them before you leave that you like the company and the folks you met and hope that you'll be a good fit, etc. A compliment about some aspect of the company wouldn't hurt either.

And look at it this way. It doesn't matter what the feedback is. If you're not a good fit, you're not a good fit. If you feel the reasons are wrong, you'll just get mad about it (and frequently their reasons are wrong, but the interview format doesn't allow for deep exploration of any candidate). If they are right, they are right. You shouldn't change your presentation of yourself based on some company's personal, biased impression. You should find a company that wants to hire you.

[wjossey]

I'll tweak this recommendation and say that I'd probably not ask outright "how'd it go" to the final interviewer (they may not really know at this point anyway). Instead, I might look to say something to the effect of:

"I'm always looking for ways to improve, and I've found in my career that interviews are a great way to expose oneself to new growth opportunities. If you, or anyone on the team, has some feedback based on the interview, regardless of whether or not I get the position, I'd love to hear it."

This has the added benefit of showing a few things:

[1] You're committed to growing and improving. [2] You're open to feedback. [3] You're showing you'd value their team's opinion, which signals your own interest in the team.

Mind you, a lot of companies won't want to share any information for legal reasons. Not much you can do about that, but it never hurts to ask.

[CodeWriter23]

I wouldn’t ask during the interview because I believe the asking could be mistaken for insecurity.

[partisan]

The right way is to position it as a learning opportunity. You ask if they have any reservations about your background. It gives you a chance to get some negative feedback and also gives you the opportunity to address their concerns.