In my opinion, MK plays standing up again after 2010 because it's what playing for a big audience is about in people's mind. If you can stand, you stand
When he had to sit in 2010 he kept explaining he had to for medical reasons as an apology of sort, I remember thinking : what's the matter with playing seated, no need to apologize. MK fans are here for the music anyway not to see him dance.
He always added in his little chat that "sometimes a little change makes his playing different", I don't exactly remember how he phrased it but that was the essence of it. So he noted a difference, not in a bad way.
Let's put it differently, Mark records his music seated if we can judge from the many session photographs , if he thought he played better standing he would record standing.
I love this thread
A bit off-topic, but it's about possible new shows, so whatever. Generally speaking, it's great to play seated, but it's much better for your voice when you stand. So ideally, one should play while sitting and sing while standing, but as Mark is a singer-songwriter, that challenges things dramatically. Then, if you want to sing well, you stand up, but playing may suffer a little. Personally, I never found playing standing a comfortable thing to do, but people are so accustomed to musicians playing standing, that Mark needs to apologize, which is ridiculous.
It's all just the idea of putting labels on stuff, the thing that Mark never been a fan of. Sitting = smaller audiences, clubs, etc., standing = stadiums and concert halls. To me, it was a badass idea when Mark played on a stool. Nobody does that! And nobody really cares.