I wasn't really posting in response to you, MrsSpectre, just in general disgust at the opprobrium heaped onto the OP, post after post.
My comment about being a waitress/asking about allergies was a bit tongue in cheek, it didn't come over that way, obviously. A poster mentioned gluten-free, and it was leapt on by followers, which would have been amusing if the spite was left out but it wasn't.
I would ask - unless there was a sign saying 'hungry' - in which case I would probably buy sandwiches/drink/fruit/cake and hand them to the person. I wouldn't expect thanks or a smile or anything but perhaps it can feel a bit awkward to just thrust foodstuffs at a person and walk away?
I've never experienced what the OP has but I do think it's a bit of a minefield. People do want to help and there is conflicting advice. Charity organisations say not to give money to people begging - but food is ok. Now there are 'professional beggars' who take away from those in need and demoralise the public from giving. It's not easy to always know the best thing to do in any given situation.
I accept that I'll put my foot in it at least 20% of the time but I will carry on doing what I do.
I don't see any issue with telling a poster that they're rude or have done the wrong thing but this thread is purposely more offensive in parts than it needed to be. Shame, because it's interesting to read about people's experiences.