However I am able to partially validate the author's point in that I too act as if Bitcoin is an investment. In fact, I now regret using it as currency when I traded almost 100 for an Amazon gift code last year.
Hmm. If you had paid it with fiat, you would have that much less fiat to buy more bitcoins, so no problem.
If you were all in with bitcoins, and wanted to buy anything, then you would need to part with bitcoins anyway, so no problem.
If you thought bitcoin's value would be tied to fiat, and therefore it would not matter to balance the position, you have a problem.