ShiroKuro I’m going to continue to be a contrarian. I mostly play for myself, but I do sometimes play for others. Regardless, when I make a mistake (especially a big one), I feel that my mental energy is really best utilized getting back on track, musically, as quickly as possible. If I worried in the moment and throughout the performance about my ‘stage presence’ and my facial expressions, that would be less mental bandwidth that I’d have for the music, and would likely contribute to additional performance anxiety and lead to more mistakes, not fewer (because my mental energy would be partially taken up by concerns about my facial expressions). I understand that for professionals, the visual aspect of the performance (whether it is manneristic movements or facial expressions, and including any visual cues to mistakes) can be important to how an audience experiences the performance. But as an amateur playing to audiences who are supportive and not wont to be hypercritical, I just don’t see a reason to add one more thing to worry about. For me, I think the music is better served if my main concern is the music, getting back on track as quickly as possible if I make a mistake, and devoting as little energy as possible to anything else that is happening at the moment of playing (including any thoughts about what my face is doing).
I will add — I’m someone who has spent almost all of my life living with involuntary tics, the most persistent/prominent of which have been facial tics. I’m not aware of them most of the time, but I know they’re noticeable to others. I don’t make any kind of deal out of the tics, and while I know they’re noticeable, it is very unusual for anyone else to bring them up to me. The tics tend to be more prominent when I’m stressed. So yes, I definitely have plenty of tics when I’m playing in front of others! But this is part of who I am, and I know that they happen when I’m playing—and very likely they really come out when I make a mistake. But for me to get caught up in worrying about them would just lead to them being more prominent. And if someone is paying more attention to my facial tics than to the music coming from the piano, perhaps that’s on me, but I just don’t think I want to give that any importance.