I used to think I didn't have much of a problem reading facial expressions.
Then, shortly after I was diagnosed, I did a few online tests. My score was miserable. I couldn't recognize fake smiles, tell disgust from sadness, etc.
I think I know what a happy face, a sad face, a surprised face, etc. look like and can correctly infer other people's general mental state if they express it, but if anyone is trying to be misleading or conceal his/her emotions I don't detect it. It's quite distressing in some contexts, because I see some people smiling and acting as if they were happy while at the same time speaking in an odd, wrong way. In such condition I tend to focus on people I know and try to get them to tell me what is going on emotionally, because I can't really make sense of it by myself.
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ouroboros
A bit obsessed with vocabulary, semantics and using the right words. Sorry if it is a concern. It's the way I think, I am not hair-splitting or attacking you.