Indeed it is an endless discussion. Either as a currency or commodity, the fact is, there are many peoples using bitcoin for various thing.
It means bitcoin is not only a currency, but a trade-able currency or an asset as well. If you can use bitcoin for trading like commodity to gain profit, why not?
It's a currency that can be use as an asset as well that's why it's a good investment but then it would prevent the merchants as well to fully accept it because of the volatility wherein when they do not exchange it immediately, there is a risk that they would lose when the price goes down since the main currency that they are still using is fiat. When the time comes that they would be exclusively using cryptocurrency then there would be no risk of losing anymore.