It is strange for (eq x x) to be false, when x holds 1, or anything else; yet that appears to be allowed when it holds a number or character.
(eq 1 1) being nil caters to implementations that have heap allocated numbers. That is fine, but under (eq x x), both arguments should be the same heap-allocated 1.
(eq x x) being nil is nothing but pandering to some weird, historic implementations, whose quirk should never have been made ANSI conforming. I don't think it's relevant today.
It is strange for (eq x x) to be false, when x holds 1, or anything else; yet that appears to be allowed when it holds a number or character.
(eq 1 1) being nil caters to implementations that have heap allocated numbers. That is fine, but under (eq x x), both arguments should be the same heap-allocated 1.
(eq x x) being nil is nothing but pandering to some weird, historic implementations, whose quirk should never have been made ANSI conforming. I don't think it's relevant today.