Wearing a suit to a technical interview is an immediate red flag. Everybody knows you don't wear suits in this industry, so what's your motive? Your ability to wear a suit is irrelevant for the job, so what weaknesses that are relevant are you rather clumsily trying to hide?

It's a red flag? Come on, if I wear a suit it's because I want too and has no impact on my skills as a software engineer.

Being hyper judgemental about the clothes people wear isn't productive

I would go as far as to say being this hyper-focused on clothes rather than if the person is sociable and competent is a red flag itself. It is rather superficial. Vague platitudes about "culture" might get thrown out, but are we engineering and building things or are we putting on a fashion show?

Calling it a red flag may have been too harsh. It's certainly not an immediate no.

However, like it or not, it is a signal because it means you deviate significantly from the mode of the distribution. And a sober application of Bayes suggests that if anything, all else equal that signal is a negative one.

I've gotten a job offer from every technical interview I ever took in a suit, so it Worked For Me. And none of the jobs that I took I ever wore a suit to again (except for conferences or trade shows, and occasionally when I was going out after work to somewhere posh, which did provoke fun "Omg are you interviewing" questions!) Which I actually have found a bit of a shame because I do quite like a chance to wear a suit, though I'm also grateful not to have to iron infinite shirts.

Admittedly I thankfully wasn't in the SV bubble where people are wound this tightly about it!

An interview is not a regular work day. If only things relevant to the job were required in an interview, no one would be talking about whiteboard exercises.

Intimidating a potential hiring manager right up front isn't usually a great play.

With reference to the GP about awkward people, if an adult hiring manager is intimidated by an professional applicant wearing a suit to an interview in good faith (after all, it's widely seen as mark of taking the interview seriously), I think it is perhaps not the applicant who need to learn the social skills.

If an interviewer can't tell the difference between a flex and show of good intent, they probably should go back to jobs where they don't need to make judgements of character.

Oh, I agree unreservedly. But if I still need to decide how to dress for the interview...

If there is a de facto dress code and you knowingly go against it, even if you look good in whatever you do wear, it makes you look like you don't understand the prevailing norms. This could lead to worries you might not align with other team norms either.

If it's so important, the interview invite should mention that casual wear is expected. Like it or not, most people take interviews seriously, and have been taught that you show you take the interview seriously by wearing a suit.

Tbh, people who blindly accept what they've been taught without considering the situation at hand don't make good engineers anyway (software or otherwise). It's not like programmers not wearing suits is some well-kept secret only accessible to the inner circle. Quite the opposite I'd say.

It's well known that programmers don't wear suits in the office in the SV. It's less obvious they shouldn't wear one in the interview either, because that's not a regular work day. It's not obvious at all to someone from a formal-dress culture like France (Italy? India?). Google's own AI recommends erring on the side of caution and wearing a suit for an SV interview. Yes, people should look up the specific company they're interviewing for... if it even comes to their mind, it's that obvious interviews require suits in some cultures.

If you forgive me the analogy, and assuming you're American, would you think of checking the etiquette of entering into a shop? In the US, the concept itself is weird, you go in, buy stuff, and leave. In France, you must greet the shopkeeper right as you go in through the door. In Hungary, you must wish the shopkeeper a good day in reply to their greeting. It's simple... if you know it's even a thing you should check.

Which is actually funny, because weren't we in the tech the people who aspired to “think different”? But then it didn't become think-different for the individual, but for the tech in-group against the square out-group. And since the world is becoming increasingly informal and any group worth its salt needs to differentiate itself, tech people might be the first to return to wearing suits and ties (or dresses) to work. I'd like that.

"Think different" was a marketing slogan used for Apple products from 1997 to 2002, back when Apple was aimed chiefly at video editing professionals. It was never aimed at techies.

As long as suits and ties remain the uniform of politicians and managers, I don't think techies will ever willingly adopt it for themselves as well.