Is it possible to write PhD thesis (or PhD level article) in Computer Science without (real) advisor? Is it possible to write PhD thesis (or PhD thesis level scientific articles) in Computer Science without real advisor (of course there always be formal one)? E.g. there are (almost) no books how to learn musical composition, artistic painting, cello playing - all such learning is done during private tête-à-tête studies. Maybe Computer Science is similar discipline which can not be learned by self-studying books, articles and conference proceedings. Maybe Computer Science has enough unwritten folklore that is passed only via direct contact between advisor and student? I have read many acknowledgments in thesis that ascertain this viewpoins, there are so much thanks for explaining one or another thing.

My question is about having real PhD advisor. Of course, each PhD student has its advisor by the University rules but there may be cases when having advisor is mere formality, advisor can have no knowledge and skills and the discipline pursued by the student. It can happen and it happens in countries that are not top countries.
Let's not lose sight of the fact that doing a PhD is a very hard thing to do, even with an adviser (and particularly in computer science, but also in essentially any other discipline). So what you're asking is basically "is it possible to do this thing that is difficult enough that a good proportion of the people who try to do it don't finish, but in a way that makes it even more difficult than it already is?" 

To use an exaggerated metaphor, it is a bit like asking whether it's possible to climb mount Everest blindfolded. The literal answer is, yes, it's possible. The practical answer is: any specific person who tries it will almost certainly fail.