I don't buy it the whole: "Tadano is completely average", because of 4 points.
1. He choose to be normal. How absolutely incredible one must be to excel exactly in the average of everything.
2. He actually can do almost everything, on an average manner (by his choice).
3. He can read minds, and communicate with those who are undecipherable. Which is out of the average.
4. As the cat in this chapter, everybody who pays attention to him see a glimpse of something more, more than average. Even the readers perceive this underline thing on the MC.