No one is going to be impressed if you burst into tears during a code review. They're going to be a lot more impressed if you bullshit your way through with positivity and can-do.
This is irrespective of the quality of the code.
This culture rewards overt displays of competitive individualism and punishes weakness irrespective of actual productivity, value, or objective performance.
Generally, being confident gets you breaks, even if you're astonishingly incompetent or just plain manipulative and dishonest.
Sometimes there's pushback from the surrounding culture before something goes horribly wrong - but just as often there isn't.
By acknowledging the possibility that you may have done something wrong, you make yourself vulnerable to judgment, and by doing so confidently you gain respect. Facing judgment is a sign of confidence and it requires making yourself vulnerable.
In a more subtle example, showing signs of vulnerability in personal relations is a way of letting others know you, and that takes courage. There'd be no point to having social interactions if you were invulnerable, any interaction would literally be inconsequential for you and thus unmotivated.
You "dress up" the vulnerability with a higher level strength (e.g. the capacity to listen to and analyze your own shortcomings), and then it's all good.
There's a difference between being vulnerable, and putting yourself in a situation that will hurt you. It's fine to show yourself vulnerable if you can do so in a way that incentives good behavior from your peers.
It gets you breaks until you reach the line which people don't want you to cross (which you will eventually cross due to your ever-inflating ego). At which point everyone you know will silently isolate you and you'll not even be able to realise what happened in time (again, due to your overly-inflated ego).
I had seen that happen. People who are full of shit always have a glass ceiling, since they are even more useless than people who are willing to directly do bad to other people (at least those are more-or-less clear in terms of the direction they take).
Are you joking? Yes - she was the CEO, but she's also facing up 20 in prison after being that CEO [1].
It's not just about getting to the top. It's about whether you'll remain there and whether the history will try to forget you as soon as it can.
Can you please edit swipey bits out of your posts to HN? Your comment would be fine without that.
I think "confidence" is rooted in the belief that "whatever happens, I'll be able to handle it. I'll be okay." Showing confidence is externally-emoting as if you believe that to be the case.
Vulnerability...I'm less sure of. I think it is the ability to be wounded. By being vulnerable, you reveal information which someone else could use to ridicule you. Patrick Lencioni's work on organizational health refers to vulnerability as a key piece of building trust[1]. How does it work? By showing that you expect that people hold a social norm against ridiculing people for the thing you reveal. That you are willing to pay a cost for that social norm. I think when people use the word "vulnerability", they mean sticking your neck out for a social expectation of compassionate collaboration -- norm-building vulnerability.
And that sort of vulnerability is compatible with confidence. If they do ridicule you, then you've learned what sort of person they are and you have the power to respond accordingly.
But I think its easy to confuse norm-building vulnerability with another vulnerability: insecurity-revealing vulnerability. This is where you present something that could genuinely hurt your sense of belonging -- Information which you think others could present as evidence that you should be ostracized from a group. For example, a man in a homophobic environment who reveals that he is bisexual. How should a man express these sorts of insecurities? By default, he shouldn't. He should hide them until he can find a supportive community. Unless he's with someone he already trusts or a mens' meeting of Alcoholics Anonymous. Don't express insecurity-revealing vulnerability.
[1] https://www.tablegroup.com/newsroom/news/vulnerability-endea... is an example, but he talks about the concept in The Advantage and his novels.