Except now how am I supposed to know '?' brings up this display?
They have rather more docs than you'd expect, the big problem seems to be that nobody expects them to have useful documentation so it often doesn't occur to us to look - hence why I figured it was worth posting it for people who didn't know about it yet.
Like I say, the big problem here is 'realising that googling "$site keyboard shortcuts" actually has a point in the first place' - hence why I tell people about '?' any time I think it might be useful :D
Most commands anyway. I'm looking at you, netcat
Either way, even an extremely imperfectly honoured convention is better than no convention at all.
Not really though. Some command in the distant past once told me that I need to type /? to use the correct parameters. And then another one told me that /? is invalid, I need to type --help for help. And thus, I was aware. Contrast this with youtube, which I use for 10+ years now, where I have 500+ videos sorted into playlists, and I even know some shortcuts - discovered mostly by accident - and never once saw the "?" help page, until I read this hacker news thread.
Anecdote, I know.