I would not mind someone saying something, but it would be better if it was said in private and then only said in a kind way.
I have trouble with my hands, and for a while I was knitting and the only way I could do it had my stitches crossed in one direction and not crossed in another. I had someone who loved the scarf I was making but when she saw my stitches she started to lecture and called other folks to comment and re-enforce how awful it was. Even when I told them why, they continued the tirade. It was in a class at a yarn shop -- I have never been back.