So perhaps it's not just me, but clearly there are two (or more) views. I agree that nature is (in general) rarely 'perfect' and that the small crossing root is certainly a normal and natural expression of the tree's growth. Although there are certainly circumstances where nature provides for a surprising amount of order and patterning (e.g. the Fibonacci sequence), most natural growth is chaotic. It's evident in the artistic or design based descriptive term 'organic', and it's understandable that a bonsai artist would with to evoke that feeling. My feeling of discomfort with this particular example is it's solitary nature. Although there are a very few other crossing or lateral roots, none of the others are as substantial nor do they interrupt the flowing lines of the trunk flare. I think that it's an interruption in flow, distracting my eye as it travels from the hollows in the roots up the tree.
Clearly not everyone agrees, and that's fine. I'm relatively new to this hobby and very glad that so many people responded to my comment while complementing this tree. I'm really happy that we can have these kinds of discussions without anybody getting crazy.
Maros, I hope that you don't make a hasty decision to remove the root based on my comment, or the subsequent discussion. I would hope, more than anything, that you choose your actions based on what you think would make the tree most beautiful.
All that said, I'm really impressed with the level of branch ramification that Maros has managed to achieve in only 5 years. The defoliated winter photo is really great. Is this level of branching (in this time span) something typically achievable with hornbeams, or is Maros' experienced green thumb playing a larger roll than normal for this species? (I have NO hornbeam experience) Are they typically fast growers / prolific back-budders?