I don't think it's down to preference as chain quotes irritate most. I'm a chief culprit of chain quoting too, but it's ultimately down to laziness with me - deleting all of the other quotes seems like so much of a chore.

I do think most of us would appreciate it if such a setting existed to enable last post only quoting. I'll have a look in the admin panel, but I'm guessing it's something Liam will have to code himself if a little button can't fix it there!