I have masks... and they undo me quite a lot. Part of the problem being and I'll use the example of my T: I appeared so measured, calm and assured when she first met me... and until I let someone in, that is what they will see unless I get badly triggered and the façade drops resulting in an explosion of emotion/anxiety/confusion/anger that can catch people very off guard.

It was also very confusing for the staff at the hospital I was recently admitted to and in for 2 months... my named nurse actually put into place that only nurses+ were allowed to discuss feelings with me as the masks I use as a defence mechanism were initiating mixed messages that resulted in panic attacks (support workers would get the impression that I was in a good place because of the face I had on and words I was using)

Edit: Just a further point though... we all (including those without mh issues) use masks. How you speak and interact with your boss, priest or similar figure (if you're religious), snooty relative, best friend, acquaintance, girl/boy on first few dates etc will be different and in accordance to the context and situation.