Looking at the commit in question, they're not only removing it, they're planning to have a new function for middle clicking:
> The middle-click will be used to start selections, and provide text contextual menus (such as word definitions, sharing, etc.)
This seems wrong. They're removing a slightly obscure feature to replace it with a completely obscure one. I wouldn't call myself an UX expert, but this seems to violate at least two important principles:
1. Affordance/User expectations: How is anybody going to figure this out, if not by accident? Worse, users who knew the middle click will probably be irritated by this.
2. Consistency: Are only Gnome applications going to support this? It very much seems like that. So their new function for middle clicking won't even work consistently across applications.
I know I'm being an armchair critic here, but I honestly wonder why they think it's a good idea.
2 doesn't really matter because other desktops might not want this at all. If they do, someone should make an effort to create a freedesktop.org standard codifying the (shared) behaviour in an agnostic manner. Can happen, but if you want to run a KDE program in Gnome you're bound to see inconsistencies all over the place. Both of them think their way is best.
> The middle-click will be used to start selections, and provide text contextual menus (such as word definitions, sharing, etc.)
This seems wrong. They're removing a slightly obscure feature to replace it with a completely obscure one. I wouldn't call myself an UX expert, but this seems to violate at least two important principles:
1. Affordance/User expectations: How is anybody going to figure this out, if not by accident? Worse, users who knew the middle click will probably be irritated by this.
2. Consistency: Are only Gnome applications going to support this? It very much seems like that. So their new function for middle clicking won't even work consistently across applications.
I know I'm being an armchair critic here, but I honestly wonder why they think it's a good idea.