... oh that's interesting. Creation of a phantom "limb" with a brain control interface? I wonder how much control there is? Does it just wiggle? Is it purely binary up/down? Can they control the angle?
I actually have a set of LED eyes that I control with puppetry, last I looked at BCIs it was woefully incapable of what I wanted but maybe I should look at this again...
Edit: The twitter link shows a video which completely invalidates my previous comment. The ears do seem to be fluidly controllable.
Previous comment:
I would assume it's just two states (ears up and ears down) that will be switched to. Most VRChat avatars I have seen do exactly this but through pressing a button rather than mind controls.
Even something simple as this adds a lot of immersion! There are probably specific faces to go with the ears as well.