Was ist unüblich in diesem Absatz?

This is an unusual paragraph. I'm curious how quickly you can find
out what is so unusual about it. It looks so plain you would think
nothing was wrong with it. In fact, nothing is wrong with it! It is
unusual though. Study it, and think about it, but you still may
not find anything odd. But if you work at it a bit, you might find
out. Try to do so without any coaching!