[MENTION=6787503]Hriston[/MENTION]'s reading, which he has made me sympathetic to, is that the halfling can vanish behind a creature - which others can't - in the same way that secret agents vanish into crowds. It leaves it open whether or not a halfling can do this while under direct observation.
Except that Hriston has now agreed that Crawford's use of "vanish" implies a change of state (i.e. vanishing entails
becoming hidden rather than
staying hidden ). For reference, see the exchange ending in
post #832. If Crawford was referring to the halfing's ability to
become hidden in the context of the previous sentence regarding being "in full view" (which I believe, given the discussion of "though", you agree to be the proper context) then the ambiguity Hriston was originally claiming (that Crawford was referring to a halfling
remaining hidden) is gone.
Is this true? I thought the general principle was that you can't hide behind your friends.
If you're not being observed, you can hide
anywhere, including an open field. Doing so won't stop you from being automatically seen once you're in full view, but, prior to then, it will require others to make successful perception checks against your hide check to notice your presence by (e.g.) sound.
So yes, Crawford saying that the halfling can
become hidden behind another creature while not in full view would indeed be utterly redundant, because everyone can hide behind anything (or nothing at all) if they are not in full view.