It’s standard behavior, so it works by default “everywhere”. Of course various software may have overridden the behavior on purpose or by mistake, so I wouldn’t read too much into what Discord in particular does. As far as I can tell Obsidian doesn’t do anything useful in reaction to the command, so it just feels like a bug.
For what it’s worth, cmd+left/right arrow and option+up/down don’t do the same thing. They behave differently with line wrapping, and when invoked repeatedly.
I’m on MacOS 10.15.5 at the moment, and in response to your comment about Discord I got curious how widely supported it is - so here’s a quick survey of a few places in the system and whether it works:
- Text Edit - works
- Editing a filename in Finder - works
- Help menu search field - works
- Notes - works
- Spotlight search - works
- Composing in Mail - works
- Typing commands in Terminal - doesn’t work, up/down is mapped to command history
- Safari search/URL field - works
- Stickies - works
- Dictionary search - works
- System preferences search - works
And a few 3rd party apps I happen to have open:
- Slack - works
- Chrome search/URL field - works
- Firefox search/URL field - works
- Figma text objects - works
- Fork - works
- Obsidian - doesn’t work
I think it’s safe to say that it’s the expected and standard behavior, and unless there’s a good reason to do otherwise, an app where typing is at all important shouldn’t mess with the defaults.