Ah, but you see, the original essay never said it was possible to be simultaneously self-effacing and egomaniacal. It stated that Nikhil is a rare combination of these two behaviors. In other words, there may be times when Nikhil is self-effacing and other times where he is egomaniacal, and this collection of behaviors over time makes him a rare combination of both.
Furthermore, though the effects of the two behaviors can differ greatly, Nikhil's essay suggests that this is a strength, not a weakness. The ability to recognize when self-effacing behavior is appropriate and when an egomaniacal attitude would be beneficial can be incredibly useful in a variety of situations. This means that Nikhil has the potential to navigate different social contexts while still staying true to himself.
Nikhil's essay doesn't suggest that one should always behave in an egomaniacal manner or that it will always lead to success. Instead, Nikhil states that his rare combination of both behaviors can provide beneficial insights in various contexts. Thus, the retort's criticism of Nikhil’s idea is unfounded - his essay is actually quite insightful and suggests that his combination of behaviors may yield positive results.
Thus, what some people might have considered a flaw in Nikhil's character could actually be a source of strength and insight. So while the retort may have disagreed with the original essay's premise, there's no denying the message: if you can find the right balance between modesty and arrogance, you may discover something truly unique about yourself!