[BinasiDombrs]

Well kendoka aren't samurai...

It is problematic to do kendo in footwear. Your footwork will be affected by the traction of the soles. The sole itself might affect the spring in the feet. And the tip of the shoes might break your opponent toes if you collide. And there is the hygenic question; when all people practise barefoot you are sure that you don't step in stuff that might have attached itself to someones shoes. Shoes can also damage the floor.

Tabi socks seems to be accepted (by some?) for practise if someone has problematic blisters or something contagious.

If you learn to tape the blisters, you can still train with them...