In a subtle way if alters how I respond to people.
While I did initially write that I wouldn't object to this so long as it was optional, and I maintain that sentiment, the above point is the one reason why I wouldn't want to see this implemented.
Responding differently based on one's sex is, in my opinion, unfair, regardless of whether or not the response contained roughly the same content.
And for the record, I very well may also respond differently if I knew the sex of the person I was responding to, whether subconsiously or not.
Just my opinion on this matter...