The 2.79 keymap is pointless because it’s legacy. It’s not getting any new tools or features.
For instance, I like pie menus. If I switch to the 2.79 keymap, now I have to manually add the pie menus in. I mayaswell just either learn the new keymap, or alter the new one.
That argument works the same in reverse. Hence why the double click to select edge loops should be on the industry standard keymap, because that’s where it belongs.
It’s an industry standard control convention. For blender’s normal keymap, again, it is redundant, less ergonomic, questionably slower, and breaks something else that works consistently.
You’re going to need an actual argument to include it, because it breaks something.
Oh look, there it is
https://developer.blender.org/T54963
