I just tried that in 3 different applications: Finder (search bar), Notes, and Slack (just in case it was an Electron specific behaviour). I couldn't get those readline/emacs bindings to work on either. This is a brand new MacBook Pro with all the defaults for the UK region so it's definitely not something I've (knowingly) disabled.
Is this something that needs to be enabled? Or is it dependant on something else to work? It's definitely a feature I'd welcome.
Weird! https://support.apple.com/en-us/HT201236 lists them
under "document shortcuts." Well, not c-u although I swear
that one worked too. Maybe they removed them and this
document is out of date? I haven't used a mac in a long
time, so it's possible. Damn shame if they did, I always
liked that feature.
[edit] A friend checked on his Montery machine and said
they work as expected in system text boxes.
