Good to know... I always made hide hard to do accidentally, anyway... Because I had the same questions as OP... Don't want to force myself to the browser to find something I accidentally hid.
People often did similar things on adjacent subs (grilling, bbq, smoking).
It was annoying because I had them all in a single multi, but generally, only up voted or commented on the one that was already most active.
For that reason, I never cross post... I find it annoying, so I don't inflict it on others...
Though, now that I think about it, posting in one community, watching for traction, then if it doesn't pick up, cross posting a couple days later wouldn't be horrible.