Me.dium - Web extension service applied to the Firefox sidebar (invitation provided)

Me.dium is a web extension service applied to the sidebars of Firefox and Flock. Its main function is instant messaging, with elements of SNS and discussion group features added. It is currently still in a small-scale internal testing phase. Since I have never used Firefox or Flock, I didn't use the internal test invitation I received long ago until today. After installation, the interface is roughly as shown in the screenshot.