For some people I want to make clear that I did not intend to state that DCC SEND should be eliminated, just that DCC XMIT should be added (even if it only allows recieving and not sending the command).
As far as the RFC goes. Yes, XMIT is not specified in the origional RFC. But that is very old now. Might I also add that file resumming is also not in there. File resuming isn't even standard, it is a de facto standard set by mIRC and a few others. Resume isn't in the origional documents, should we get rid of that?

I have yet to see significant a reason not to support it. Other than the fact that some people are afraid of change. Of course you should keep DCC SEND but there is no reason not to add support for DCC XMIT.
Why not?

I'll tell you why... faster and more streamline transmitions and complience with cutting edge clients. Stop adding new features to the protocal and I guarentee you that in a few years mIRC will no longer be the leading IRC client. Even if I am wrong, why risk it?