The "it" in the phrase "it is not so" relates to the phrase "spending bitcoin is economically irrational". It is economically rational to spend bitcoins because

The "it" in the phrase "it is not so" relates to the phrase "spending bitcoin is economically irrational". It is economically rational to spend bitcoins because a person wants to enjoy some of her wealth before she dies. That is the only reason I have sold part of coins I mined in 2011.