Hah, yeah I seem to remember Ctrl-S leaving me flustered for quite a while when I first stumbled on it!

You'd probably trigger it more often if ~/ didn't conveniently map to ~/ - it's quite cleverly designed in a way. Indeed, most of the two-character combinations you're likely to type starting with ~ map to themselves.

Yes, it's a good choice of characters.

Specifically, the escape sequence is "\n~", with various options (visible by typing "\n~?"), and if the option is unknown it passes the "\n~{x}" as-is.

The biggest false positive you'll see is "\n~v", when executing bins out of the home dir of a user starting with the letter 'v'.