Sentence rewritten to be convoluted:
"Self-absorbtion could be the real explanation, as I may have mentioned before, regarding certain people's perception of their personal quality in the area of empathy, specifically their supposed superiority in that regard."
"I have probably mentioned this before, but if you think you are unusually empathetic, the chances are that you are actually fairly bad at empathy, but are too self-absorbed to notice."
It is not the length of a sentence (or paragraph, chapter, etc...) which makes it convoluted. Rather, it's in the flow of the ideas. A sentence will be more difficult to understand if the reader must hold several supporting ideas, or even a conclusion, before the author has delivered the subject being commented on. A logical, linear progression of remarks is easier to follow.
Or, to propose a metaphor, if you start building a building from the roof to the floor, you have to hold everything in suspension until the foundation is put in.
Some ideas, admittedly, are not linear concepts, and finding a logical order of presentation can be challenging, or even impossible. But in most cases, it is possible.