As the OP mentions in the question, there are plenty of out-of-universe statements regarding the glove, such as this one from Nimoy himself:
NIMOY: We were looking for something that the character could wear that was distinctive and immediately recognizable. I got the idea from a friend who had a badly burned hand and wore the leather covering.
But as for in-universe reasons for wearing the glove, I cannot find a canon source that explains this.
Given the lack of information, I will offer my own speculation on the "deeper meaning" of the glove.
As Nimoy recounted, the original purpose of the semi-glove was to conceal (namely, his friend's burn) rather than to, say, keep the hand warm.
From this, I suspect that the deeper meaning of the glove — if there is one — is that it points to the fact that Dr. Kibner is concealing something. (And of course, he is.)