Edit: of course, you could say the same about other digital transmission of currency, but it seems different due to bitcoin not being tied directly to any "real currency". Then again, IANAL.
With this message, I hereby transfer to jnhnum the sum of $12.54 out of my checking account.
(Translation, since that's probably a bit subtle to just throw out there: In the process of abstracting money transfers as "just sending messages" your abstraction has leaked critically important details. There's more to money transfers than "just messages", and it is precisely those differences that are why you will not be finding $12.54 from my bank account in your account as a result of this "message" that I have just sent. Your abstraction is not a good one for any purpose, practical or rhetorical.)
If you had liberty dollars then you'd have money.
To directly answer your question, money becomes currency when you transfer representations of value instead of value. (eg. A piece of paper obliging the barer to receive something of value)
Pennies, especially pre-2000 pennies would be considered money as the store of value is the metal not the face value.
"Money is any object or record, that is generally accepted as payment for goods and services and repayment of debts in a given country or socio-economic context."
This is in line with most actual usage of the word. Bottom line, you're just playing silly semantic games. It is useful to understand the differences between different types of money, but claiming that something is "not really money" based on your own private definition of money does not add to the discussion.
Most people think that playing the lottery is an investment strategy for retirement, I would not trust what most people think when it comes to economics. Little semantic games are hugely important to people. Look how pissed everyone gets when MS describe the MSPL as 'open source'.
Actually, my own private definition does add to the discussion, when enough people connote a word to have a different meaning it changes the definition of a word, all based on their own little private definitions of words.
Your views on semantic contexts are 'fantastic'. I'd suggest you look that one up on the OED if you want to understand the definition I'm using, most people would get it wrong.