This is proper and expected, right? I mean no one's going to be angry with you touching the original line? I've never had to share a cleat (ie not a sailor... yet).
Dipping the eye just places your line under your neighbour's. Even if you put it on top they can do the reverse to get their line on top and out without removing yours. Would have been nice for you to show the reverse as well.
I noticed that, too. yes, your line would need enough slack to get their eye through yours, but then once it's over the top of the bollard it'll drop straight through. i grew up with cleats though, so, this is me seeing this for the first time
