i feel like it isnt really possible to ALWAYS be doing them when its not actually what your feeling. but very good actors can do micro expressions that are written into the show, i believe. most people would not detect them, though, unless they were made very obvious.
of course they do, dats called 연기 ! :) what i'm trying to say is dat when ur 연기 ur portraying another person and 당신 have to show the audience your emotions, your feelings and of course your micro-expressions are part of all dat!
