As another short person, I think the OP may have meant their feet were straight down from the seat, directly in front of the bar, not behind it - I'm not sure it's physically possible for a short person to put their feet behind the bar.

I've had problems with being hit in the ankles by the feet of a very tall person seated behind me which were all the way over the bar. I politely asked him not to stretch into my space and to stop kicking me. He was a jerk and told me he "needed" to stretch his legs all the way forward and that I should keep my feet out of his way. At that point I let the FA inform him his space ended at the metal bar, not beyond it.