If gold is a currency then I would be able to take a few gold...

If gold is a currency then I would be able to take a few gold coins to Coles and buy some food. But you can't, as was proven in Iceland after their currency collapse. The people with their savings in gold were better off than those with money in the bank, but then so were people who owned platinum, diamonds, copper, silver, barrels of oil, US dollars etc. But you still couldn't buy anything unless you physically took your gold to another country in Europe and sold your gold there for euros and then took the euros back to iceland.
The local currency was worthless, and access Euros/foreign currency was restricted.
Hence why I consider it a comodity, because you can't spend it, you must sell it.