I posted about this before on my blog. I wasn't being asked the generic, "How are you," but actually being told/asked, "You look expressionless. Is everything okay?"
When I'm expressionless, I'm usually also in my blessed thoughtless state, which is rare for me, because otherwise my brain doesn't usually shut up. So being asked that is like an AED jolt to my brain that gets everything back up and running at full speed ahead. It really annoys me, even though I know the other person is just being concerned.
Regarding emotions, I run hot or cold. When I'm cold it's LIKE alexithymia, but it isn't actually alexithymia because I do still have emotions - I'm just not talking with them in that moment. I can always identify my emotions when they are running hot, because they are usually also running pure, so I'm not getting confused with multiple emotions at the same time. It's when they are lower level and confusing that I want to turn my emotions off.