I've heard alot of these too. I was extremely skinny as a child. Now, I'm still very thin, but more athletic. I do still get comments.

I think because society once revered the heroin chic skinny, people think it is acceptable to comment on peoples slimness.

I would never comment on someone who was larger than me. I would never call someone fat or any derogatry comment related to weight. Yet, many people think it is ok to slander someone for being slim.

I used to be called a "skinny C*nt" by a work colleague. It was all in jest. But he wouldn't have got away with calling someone a "fat c*nt"

I experienced alot of boob shaming too. I wrote about it a while ago if you are interested. Medium readers loved it, it garnered quite a bit of attention :-)