so we know if we're talking of a real or a purely theoretical issue.
It'll become a real issue as soon as it starts actually mattering. If you're small time nobody cares, if you start getting big time you won't find an accountant to sign on your stuff.
For individuals it doesn't matter that much.
Until it starts to matter.
If you're doing business seriously you need to consider all foreseeable risks, and that is one of them.
Because just because you didn't get in trouble today doesn't mean the taxman won't come tomorrow knock on your door and bash your company to nothingness.
This raises the question; what's the threshold for being considered a 'professional' seller within Finland?
That would be specified in the law, in France for example it's around 50kEUR/year which is not much.
In addition, at least in Finland, you seem to be indicating that the current rules preclude any business that actually buys and sells Bitcoins in the same way as Foreign Exchange dealers such as 1st Contact Forex, Transferwise etc do for currency exchanges.
You do not reason with the taxman by using common sense, you use laws.
To casual an extremely paranoid observer it might seem that these punitive taxes are being applied to seriously stunt the spread of Bitcoin to the mainstream.
FTFY
There actually is one correct and sensible way to handle this situation, it is to use the procedure that is present in France (and I assume every civilized country), to ask the tax administration for a formal and binding opinion on a very specific question. In France it's called a "rescrit fiscal" where you ask the taxman to clarify something and take a position. That's where you need to word the question extremely carefully :-)