Speaking for myself, I am not good at reading body language of other people, but it also seems to me that other people are not good at reading my signals. (Maybe the abilities to "read" and to "speak" the body language are related. Is there a research for this?)

There are probably cases where body language is actively spoken in a way that's learned. On the other hand there are people with Asperger's syndrome where I can tell based on their body language that they fall in that spectrum and are therefore unlikely to be very comfortable with a hug.

They can still make a conscious decision to want to want to hug and then that's really hard to read.