Part of becoming a great engineer, in my limited experience, is developing a sense of taste for what problems are worth solving and which approaches to consider.

The software we build ends up baking in those opinions: into the frameworks and libraries, into our philosophies, into the algorithms themselves, and ultimately into our culture. We end up with Rails whose claim to fame is being based, unabashedly, on its strong opinions. We end up with the LKML being what it is. We end up with ML algorithms with our biases built in. That's why our opinions are rather important.

Our opinions signal our status to other groups. If you're an opinionated statically-typed functional programming aficionado it's quite likely you're not going to fit in with people who are serious adherents to object oriented programming. And you will find many people without any opinions or whose opinions lie somewhere in between.

We can't avoid having them and it's important to be able to work with other programmers and so being able to set those things aside to focus on the customers' needs, the business context, and the well-being of your team takes precedence!

Not OP either, but I think what OP means here is that programmers feel that their own opinions are more important and refined than anyone else's, even other programmers. This means that they are likely to judge someone who operates in a way that differs from their opinion more harshly.

A bit of that too.

Because they're building it, it's more important. If you want to build along vector X and they believe in Y, you'll only get the projection of Y on X in business value. So if you can convince the people making things to make something closer to X and you can articulate that value and excite people about it you'll get a bigger projection.

The refining part I don't get.

Not OP, but my stab: programmers are the ones actually building something. A technical leader can craft a vision for the technical future of a product, but the engineers need to buy into that vision and will, by necessity, quickly form refined opinions on the implementation details as they build things.

I've wondered this as well. Are there equivalents in other industries? Some human trait that shows up in some circumstance?