To answer the first part of your question, for me, I'm uncomfortable with the idea of "impressing" others. My approach in life is the antithesis of impressing others and I will sometimes downplay whatever intelligence I supposedly have. However, if over time from knowing me, someone comes to regard me as intelligent, than I would feel grateful for that regard.
What I'm trying to convey is that I'm the last person to get up on a soap box and show off. It feels uncomfortable, in the sense that my ego is running wild and in some childish way I need approval from others. At the same time, I do like to be respected, and one of my best attributes is my intelligence. Does that make sense?