I don't mean about:config, I mean editing the CSS directly.

Yes an update could break your CSS fix, but if you follow the beta releases then this isn't a problem. You usually have at least a few weeks to update your patches before the release goes out.

You have to change a setting in about:config to enable custom css. Unless you mean making a custom build of Firefox, which is even more difficult to do.

I don't see what difference it makes for somebody else implementing it as about:config setting versus you doing that yourself in a custom build. Firefox is not really any more difficult to build than any other large open source project.

Is that something you would expect a typical user to do? Especially users that aren't developers?

> Firefox is not really any more difficult to build than any other large open source project.

That has not been my experience. Granted, chromium also has a very difficult and slow build, and browsers are big complicated things. But my point is it isn't easy.

In my personal experience, typical users (i.e. non-developers) don't really spend time tweaking their browser. The defaults are good enough for most, and the job of the developer is usually to just find good defaults to optimize for that. For the power user who knows XML/CSS/JS/C++/Rust/etc and wants to have total control, then yes, I would expect them to either create extensions or edit the source directly. Same thing goes for Chrome users of that type. Am I off base here?

It's true the build process is slow, but that's different from being difficult. I don't know what you mean by difficult. Maybe it was difficult in the past but it's entirely automated at this point. You can just start the build and come back some hours later, and that's only if you're starting from a clean repo and modifying the C++/Rust. For the CSS and Javascript, that doesn't need a rebuild at all.