Traditionally, for a man among men, expressing confidence has always been safe. If a man expresses confidence in a situation where confidence is foolhardy, other men will interpret it as a performance of masculinity. I'm sure Rick understands this project is going to be a nightmare. I'm glad he's gung-ho about it. If you express fear, on the other hand, your fear will be scrutinized to determine whether it is well-founded and appropriate to the situation. I'm worried about Rick — he seems terrified by this project. I know it's going to be tough, but geez, grow a pair.
Women among women are in the opposite boat. Expressing vulnerability is always safe because it can always be read as a performance of femininity, but expressing confidence invites scrutiny as to whether it is well-founded or arrogant.
Both of those scenarios have a safe fall-back based on gender expectations. When you mix genders, the fall-backs disappear. In tech, this is virtually always a problem faced by a woman in a male-dominated workplace. If she's ever momentarily in doubt, there's no safe direction to err. She can't take the masculine safe route and project bravado, because that behavior only reads correctly from a man. Nor can she afford to fall back on traditional expectations of women, because traditional expectations of women would suggest she isn't competent at a technical job. So she has to hit the correct balance of confidence and vulnerability every time. There's no safe fallback.
And even when she hits the correct, situationally appropriate balance of confidence, the men around her might still be confused about how they're supposed to interpret it coming from a woman. Unless they analyze her confidence in a rational, point-by-point manner — and how often do you do that in a workday? — they're relying on instincts that are conditioned by cultural processes largely outside their control to 1) expect confidence from coworkers and 2) not expect confidence from women.
Anyway, it's pretty disheartening to see an incident that is heavily colored by gender expectations related and acknowledged as such but then interpreted as a story about a one-dimensional spectrum from expressiveness to guardedness. A man in the same situation would have been allowed a generous expression of confidence and self-regard, even if it reflected less technical insight than the woman's fears did. Women and men both routinely filter the emotions they share with other people, sharing some and repressing others. Showing vulnerability isn't about being unguarded or guarded, or about naive "authenticity" versus Machiavellian "performing authenticity." It's about filtering differently for a different set of expectations. Nor is it about women not understanding that personal knowledge can be used against them. Witness teenage girls feeling forced to suicide when other girls use their secrets against them. Women are not (and cannot afford to be) less socially careful than men, or less aware of the dangers of sharing.
Nor is it true that "if you are ambitious, all of the top jobs are reserved for people who are closed and guarded." Successful male leaders are rarely cold fish and are often very personally charismatic. They have to be mindful of the effect their expressions of emotion have on the people around them, and of the necessity of using that power to inspire loyalty and sacrifice. You can't make it to the top without inspiring trust in people. In case that sounds overly touchy-feely, let me add that it's especially important if your ambition requires other people to fail. It's easier to knife someone in the back than take them head-on. The "closed and guarded" person is never going to enjoy someone's loyalty or take a rival by surprise, because everyone is going to treat him like a snake. (That's one path to power, but judging by the people you see in high positions, it isn't a common one. Even Donald Trump projects a lot of interior qualities such as confidence, defiance, and self-regard and inspires loyalty in people who feel that he is gifting those emotions to people who need them.)
On a final note, I suspect the author understands 90% of this but is stranded on the wrong side of the enormous dichotomous wall he has erected between authentic emotional expression and manipulative emotional performance. People always filter and selectively amplify the emotions they express. That filtering is not inherently false, malicious, or untrustworthy. It's an inevitable part of being human, another complication when understanding another human being. A person's filter can be a positive or negative aspect of them, something they use in constructive or destructive ways. That's a better way to evaluate this question of vulnerability in the workplace. What kind of filter do I want my employees or coworkers to have at work? Should we systematically favor bravado over vulnerability? My gut feeling is that we should not.