Shit. Didn't think about that. Does that really happen, in practice? I would have thought that it would take some pretty good pedalling force to undo a pair of pedals that were on tight. Correct me if I'm wrong, however - I just thought it wouldn't be an issue.
The turning force is only that of the friction in the bearings. In practise I doubt it. Over time though, maybe they'd loosen. Who knows. There's a reason why left and right pedals thread differently though
You'd also be slowly unthreading your pedals running cranks LHD