Both Chrome and FF have plugins to add vim key bindings - at least for navigating around the UI and the page. Which would support the argument to learn them. I guess your argument would be stronger if there were other $editor_of_choice key bindings for browser textboxes?
There are key bindings for other editors, they're called CUA :-)
I can Ctrl-C/Ctrl-X/Ctrl-V to copy/cut/paste, Ctrl-arrows to move around one word at a time, Ctrl-shift-arrows to select words, Home and End to go to the start and end of the line, etc, Ctrl-Home/Ctrl-End to move to the start and end of the text input, etc.
Those are emacs bindings. Readline uses emacs bindings by default, but it can also use vi bindings.
Unless you mean that it uses readline and so configuring it (i.e. ~/.inputrc) allows you to change the keybindings of macOS UI text fields. That'd be cool if it's the case.
I have a big issue with these bindings: there is no "right" ctrl on my MBP keyboard. If you touch type, I find ^A very cumbersome to type. I find it easier to use mac os default (cmd + arrow) which also opens variants such as option + arrow, shift + option + arrow. The only readline binding I do use is ^K (not as bad as ^A because k is on the right side of the keyboard, and there is no alternative anyway).
