While trying to remove an item from a private market I issued an order to buy 0 at 0 stellars. It was reported as follows :-
>Date 5.2: Market Buy {30311} {0} {0} {private - Yes} {Add to Market - No}
Buying 5000 Greater Ground Birds (30311) at 0 stellars each
It seems to have worked OK - what is reported is just a bit misleading though.
I've also seen this several times, but as long as either number or price is zero the order works...
I wonder though what happens when both numbers are changed...