Aside from making the knife itself less visible, you could still see the clip, so what benifit is there to gain from this, aside from personal preference?
I'll just start right off by stating I haven't read anything but the original post, so what follows might have already been stated - perhaps more eloquently and thoroughly.
The purpose of a deep carry clip is, primarily, to reduce the overall profile of the item you are carrying. A clip is one thing - it is somewhat notable, but perhaps only if you are looking for it. A bit of handle, however, tells the observer quite a bit more - there is no doubt; it is the unmistakable profile of a knife.
To hobbyists, seeing a knife in semi-concealment is nothing untoward, but the vast majority of the populace sees a folding knife as a potential weapon - which means that visibly carrying one can be grossly misinterpreted as a kind of indirect threat or assertion of power.
While many carry a knife for the purpose of addressing everyday tasks - like the vast majority of us on this forum - the day-to-day citizenry of the world typically see little justification for carrying anything beyond a swiss army knife as justifiable preparation for such tasks. It's a frustrating truth that carrying anything beyond what might be the absolute minimum is easily misconstrued as having some sort of untoward intent.
While most of us here understand that nobody is going to drop $100+ on a knife that they intend to use for an injurious activity towards another human being, the popular perception of knives is overwhelmingly negative; people don't see them as cutting tools - they see them as weapons. So, for hobbyists and general folk that carry folding knives, discretion is valued. Deep carry has a function of a sort of social plausible deniability. Minimizing immediate visibility has real value when the alternative is answering the question "why do you have a knife?" - to which, any answer can seem defensive or suspicious.
