The level of confidence with which people express themselves is a (neutral to me) style choice. I'm indifferent because when I don't know somebody I don't know whether to take their opinions seriously regardless of the level of confidence they project. Some people who really know their shit are brash and loud and other experts hedge and qualify everything they say. Outward humility isn't a reliable signal. Even indisputably brilliant people frequently don't know where their expertise ends. How often have we seen tech luminaries put a sophomoric understanding of politics on display on twitter or during podcast interviews? People don't end up with correctly calibrated uncertainty unless they put a ton of effort into it. It's a skill that doesn't develop by itself.