I had a few PMs with GazetaBitcoin on this issue and that was my answer:
[GazetaBitcoin asked about my opinion on this issue]
Bitcoin (BTC) = Bitcoins
I know, it's highly controversial what's a Bitcoin / what are Bitcoins. Some people might refer to it as "coins", some might refer to it as undefined mass or even more technical an allocation of utxos (unspent transaction outputs).
For now, I assume "Bitcoin" is most suitable.
In my opinion it is indeed very controversial (because in Germany, we always write capital letters) but I would always write Bitcoin. After all we know what we are talking about.
If we make it totally accurate, we could say: I just initiated unspent transaction output(s).
BTC