Great article. I always loved the approach of having each component manage its own CSS/fonts/images and this clearly lays out how to achieve that with Webpack. Will be very useful in my next project.
The post-css stuff is really great too!
I don't know that I like it. First of all it's a pretty simple task - take me to the top. Users can scroll but they want to get up there quickly. This script makes that process slow and it's not like you can read content on the way up without straining and getting some headache. Furthermore you can't cancel it half way through - it completely hijacks the scroll wheel.
I have my own built on top of RequireJS/r.js and Grunt right now. I think Webpack does a lot really well. Never used StealJS, heard bad things from the past.
Most module loaders nowadays support all module "formats". RequireJS is a weak comparison because RequireJS is one of the earliest module loaders and attempts to solve the problem in a very specific manner. Furthermore, supporting many module formats is unlikely a perk for any dev team. It just speaks more about "ok I can use this for my system". Most dev teams have coding conventions and stick to one format throughout the project life time.
Bigger bonuses to me is being able to consider images, fonts, and CSS as modules. That way my front-end codebase can be fully modular.