This sounds like a cartoonish training example of the kind of subjective, possibly biased feedback that you absolutely shouldn’t be writing down as an interviewer.

A somewhat comparable analogy is your manager joking about firing you and then evaluating you negatively when you don’t like the joke.

“Oh hey jumping between languages is hard, looks like you’re thinking in Swift right now, no worries about fumbling on syntax happens all the time”

My impression from the OP is that they were out of sync with their interviewer, they didn't "click". This is something that happens with humans. The interviewer may have detected this dynamic, and made the joke to break the ice. Obviously it backfired, but with another candidate perhaps it could have saved the interview?

Separately, what do folks thinks about the importance of humor on teams, and the degree to which it's acceptable to screen for sense of humor as part of interviews?

Here is how I see it. At best, you interrupt a candidate in the middle of a technical interview to make a joke. At worst, you ruin the interview experience for the candidate. To me, the cost/benefit is clear cut.

During a technical interview, you are evaluating the candidate’s technical knowledge. You are not there to become friends. There will be time for that after the candidate goes through the interview process.

The only other choices for the interviewer are to bluntly say "you missed using semicolons" or to not say anything and be left to wonder if the person knows how to really write in C. The author of this post seems to think even considering any other choice than the last is rude since "whiteboard code doesn't compile so semicolons are syntactic sugar".

But if it does matter, baking in some understanding of the charitable reasons why (that the interviewee is proficient at multiple languages, especially in the popular ones at Apple like Swift) is actually the nicest thing the interviewer could have done.

The post author seems to me hostile to being corrected. Given that every code review I've been in requires being corrected dozens of times about errors large and small, I wouldn't want to have to deal with their uncharitable attitude towards feedback from coworkers/collaborators.

Code reviews after already being hired and accepted into a company are not comparable to interviews during the application process, when the specter of rejection still looms.

Anyhow, to answer you, on both sides of interviews, I've experienced bad chemistry early in the session. Could be any number of factors, even just one of the two of us getting out on the wrong side of bed that morning. I sometimes will make a joke to lighten things up and get things back on track. Sometimes it helps, sometimes not, but I like to feel over time I am learning better how to interact with humans, and improving my odds, leading to more positive interview experiences and less wasted time. Things are never "strictly technical" with humans.

(all that said, to be clear, I have never brought up the candidate's sense of humor in providing feedback, although I don't see a problem doing so if humor is in the team's values manifesto or the job description, and we've agreed on a legitimate way to screen for it (seems hard!). Curious to learn others' thoughts on this subject!)

1) felt that the tone of the interviewer was negative

2) was in the middle of writing their solution

3) did not actively ask for feedback on syntax

Point #1 is subjective, but an interviewer should err on the side of caution when making curt remarks like this. Taken together, points #2 and #3 are important too: as an interviewer, you should know when (or even whether or not) to provide feedback.

As for why I believe the comment above phrased it better:

1) the interviewer is clearly acknowledging that it can be challenging to use a different language in an interview

2) the interviewer is clearly stating that the syntax mistakes being made are minor and nothing to worry about

Personally, I would still avoid making this kind of comment unless prompted by the candidate - e.g., in reply to "I think I might be making a few mistakes with syntax here". I would also avoid providing any feedback.

I also agree that an interview is not purely technical: there are other _passive_ signals you can use to build a better picture. I don't see how you would be able to judge sense of humor reliably in an interview setting, though.

A negative reading is “you are screwing this up enough for me to comment, you need to justify why”

If it’s intended to be reassuring then phrasing it so it’s clearly not a criticism is better. If it’s intended as a criticism then phrasing it clearly is also better.

The way I can see it being a joke, as claimed, is insultingly. Like a dentist watching a trainee dentist doing a filling and saying “you must have been doing masonry work lately”. Haha but the subtext is “you’re really doing a bad job of this”.

Good for you I guess, but maybe don't apply your own mental blueprint to the rest of the world. Recommending candidates have thicker skin isn't really great a way to improve hiring in general.

It does sound a bit annoying, but if that is the author’s worst interviewing experience, it’s not that bad.

at a point in my career i faced a similar dilemma but handled it completely differently than i had earlier. someone made a snide comment "but why would you use bash for this?" and i was able to take it in stride and the result of that comment got me the job. but at the start of my career i may have reacted negatively, i may have clammed up and stammered my way through the rest of the interview etc (i didn't get those jobs). could you imagine being in front of a C-level exec or a $300M customer and being discombobulated?

no one wants to hire an insecure pre-sales engineer etc

EDIT: i'm assuming engineering levels beyond senior. my past experiences have been around principal/architect roles which require a 'tough skin'. i would not expect rude remarks to a SE1 or SE2 and if that was the role, i would leave flustered with a bad taste in my mouth as well