its neither an asset or a commodity though its a currency, and its dosn't even need to be backed by labour because its backed by a computer
network that cannot even be matched by any amount of physical labour
even if we ignored the tax classification...
bitcoin is like intellectual property, art, graphic design, game code... which (nothing related to tax) still puts it in a description of an asset.
that being said an asset, commodity, fiat, or ANYTHING else can ALSO be a currency.. so relax, bitcoins is a currency and an asset.. it just is not a commodity..