[voxic11]

If GP is an asset with real value then acquiring it is taxable as income, no different from if you acquire bitcoin via mining. I really don't think video game players want to record every GP they acquire and file taxes for it at the end of the year. So a legal fiction of it being non-valuable is still probably preferable by them even if it excludes them from some legal recourse in the case of theft.

[roryirvine]

Tax would only be due on any net gain that's made, surely?

[voxic11]

Well yeah, but that just means you also have to record both the GP you spend and the GP you receive and the fair market value at the time of spending or receiving it.

Unless you are thinking that you only would need to file taxes if you were to sell the GP for some kind of normal currency. That isn't how income tax works, you can't avoid or delay being taxed by receiving your salary as gold or bitcoin or some non-currency asset, all "clearly realized accessions to wealth" count as taxable income. And so just as you have to pay income tax on the fair market value of bitcoin or gold whenever you mine or otherwise earn it, you would also have to do that with GP whenever it was earned.