@OP you are not thinking about this in the right way.

Just because its called a bit"coin" does mean it's money.

You can't use it to pay taxes.
It is not recognized as a currency by the BIS
Almost nobody accepts it in payment. Try "paying" your accountant or tax adviser in bit"coins".

By the way, I'm also eating some chocolate "money" as I type this.

BTC are simply a virtual good. Like a lot of people you seem terrified of the law and or government...this should tell you something about the system you live in.

If you held a World of Warcraft character that "appreciated" from $200 to $600 dollar, would you have to declare this? Don't tell me its "illegal" to sell your Warcraft account....it IS however against Blizzards "Terms of Service". Other online games *allow* trading of virtual goods. People in EVE online sell Pilot Extension licenses all the time, and this is endorsed by the Company (CCP). The value of Pilot Extension License changes all the time....you DONT have to declare a "capital gain" in your pretend on-line spaceship to the government.

Bartering is not illegal (yet....lol), you can therefore swap your virtual good "bitcoin", for a real good or another virtual good.....no USD necessary. The only problem is when you decide to "Cash Out"...by doing this you are basically showing that you don't really view BTC as a currency (why the hell would you sell it if you thought it was a useful store of value and appreciating).

If you do cash out into Federal Reserve notes, you've now entered the Feds juristiction, you probably DO need to pay capital gain.

By using bitcoin it helps you see the inherent corruption in the USD system. Everytime a  USD moves, the Feds take a cut of it, in effect they are extracting the value and essence of your life and work. If bitcoin takes off, why would you want to use the crappy Federal Reserve USD system which is designed to steal your wealth and transfer it to the elites.

An interesting point in history, according to Benjamin Franklin, the main reason the British went to war with the States was over the fact that the States was issuing its own currency, thereby cutting London "out of the action" as it were. No British pounds used, no Loans in British pounds, people trading in third party currency...how the hell were the British Elite parasites gonna get their "cut" of the Americas wealth? The sad fact now though is that  under the Federal Reserve, the American elites are just running the same system to transfer wealth from ordinary Americans to themselves.