Yes the magic command is copy twice within 5 seconds. It can be cmd + C via keyboard or context menu copy, anything updates your clipboard twice with identical content will be triggering it. You can always disable it conflicts with other workflows or apps.
I use ClipMenu to save clipboard history and will often copy a bunch of things one right after the other, and can use other shortcuts to easily select whole lines or expressions in my editor, so time between copy could be as little as 750ms I'd bet. Is the timeout configurable?
Yes it's configurable, between 1-10s, defaulted to 5s.