This is a change also made by R6RS, specifically:
A quasiquote expression may return either fresh, mutable objects or literal structure for any structure that is constructed at run time during the evaluation of the expression. Portions that do not need to be rebuilt are always literal
This proposal stems from remarks by Alaric Snell-Pym and Will Clinger on the r6rs public mailing list. If eq? is allowed to return #f on two procedures when eqv? nevertheless returns #t, as is already the case for numbers and characters, then more intelligent implementation-specific procedure comparisons using eqv? are possible, while still keeping eq? simple enough to inline easily.
Note that this is orthogonal to the question of #460, how eqv? works on procedures. There should be little or no backward-compatibility hit for this change.