Ahh! Another spirited debate resurrected!
I'm lucky in that my boat has LL stanchions exactly where it needs fenders. I've been tying them at the base with a clove hitch (or some sort of multi-hitch barf) but just bought brass clips to allow 'anyone' to simply wrap the whip around the LL post and clip it to itself. Both fenders hang within a fraction of an inch of each other, so there is no 'wrong way' to hang the two.
The above is fact; below is opinion.
The Navy taught me that life-lines are for just that; not for leaning against or hanging drinks from. I still do it, but at least I feel bad. I do agree that fenders shouldn't be hung from them. I think it is too much stress and it goes on 24/7 when the boat's tied up.
My brother slipped on deck years ago, broke a rib (or two, who X-rays anymore? It's so eighties.
) and would have rolled into the Bay if the life-lines weren't there for him to grab. It's only an anecdote, but still Thanksgiving is more fun with him there.
I would like to close by saying I would only clip my fender whips to the life-lines if I were going down the ICW without an engine.