It is a fact that people listen to some music to show off, feel important and smart, show to their friends and strangers on the internet.
But how come this website talks so much about this? Is this such common phenomenon?
Or is it that the people who enjoy a sound so much, find out there are others who do, and frequently share with them, without that meaning that they are merely following guidelines of popularity/uniqueness to gain attention?
To answer your first question - it's more common than you would think. Most people do this unconsciously, actually. The "show off" part comes when they're with a group of people; social behavior rarely is the same as behavior alone. There are entire scenes which exist around this, look at all that fashion/crunk-core bullshit like Brokencyde that was popular a year or 2 ago; that scene was entirely transient and a fad but people who liked it didn't care generally. Same deal with the modern hip hop scene, it's no longer about crafting poetry to a beat, but about "gettin' paypuh".
Most people aren't cognisant enough to realize that they are participating in a social group when they like these certain kinds of music. They simply think "oh hey these people like the music I like, cool!" The problem is that most of these people don't "enjoy the sound" on a level which could be defined as appreciation. They're concerned with aesthetics. Does it immediately grab your attention? Is there a phat beat, or a neat sample, or a strange hook? For many, this is what characteristics of music they latch on to. They don't have the capacity (or haven't discovered that they do) to appreciate music on a deeper level, since all they're concerned with is surface elements. I believe this has been covered by this site in retaliation to people "just enjoying it, man! don't be such a downer!" which you argued for (seemingly) in your last paragraph.
I've said it before and I'll say it again, you can like whatever you want. Personal taste is almost entirely subjective. But good music that deems respect and appreciation? Not so subjective.