The masks of inscrutability, or are you really you?

[the phantom]

But why adopt a nickname at all, than? If you is you and Aiwendil too, why not choose your own name as a nick?

There is no reason to. Your name only means something to people who already know you. If I would've signed up as "Philip" on this site, it wouldn't have meant a thing to other members. Since that's the case, why not pick some other name that sounds cool, tells something about you, or is Tolkien related?

Yet the person under the name HerenIstarion exists on the net only. It is a mind with no hands, no body, but words only. I believe medium impacts the thing which operates through it – hence, HerenIstarion is different from what George Lashkhi usually is.

Maybe that's the case for you, but not really for me. the phantom has a real physical body that exists outside of the net. I have real life friends who call me "Phantom", and I have met a few other Barrow-Downs members face to face and they still call me "Phantom". In my case, my screen name seems to be synonymous with my real name.

That passion, though sometimes may shine through, is hard to communicate through keyboard and screen

That's what smilies are for, silly.