I had a guitar teacher once who pointed out to me that the best guitarists kept their finger movements to a minimum, thus conserving energy, and making it easier to play quick passages more easily and fludily.

Last night at band rehearsal, I noticed for the first time that I closed my eyes. I didn't like that, even though I realized it helped my concentration. I think I'd like to break that habit if it follows me onstage. As far as closing one's eyes while singing a comic song, I think I'd rather not, particularly then. I like to accent the joke lines with facial expressions. In other words, if the song is funny, the expression on my face should reflect the mirth of the lyric. Sorta like an actor would do.
Jim