Did you follow his little demo? Let me see if I can explain it. "Killing" in Emacs-jargon is similar to cutting (ctrl/cmd X). Holding control and pressing "k" (C-k) deletes the text starting at the cursor (point) up until the end of the line, and puts that text in a buffer. It can be pasted (yanked) with C-y. In Emacs, killing multiple times without any other movement between kills appends each bit of text to the buffer. If you move between kills the buffer is wiped out, and subsequent kills put the killed text into a clean buffer.
I think he basically wants the kill buffer to be wiped out when you move between kills. His demo shows that in OSX text fields this is no longer the case, and at least on my machine running 10.6.something this is true. Emacs of course still behaves the way he wants.
That was actually a great explanation - to clarify a bit, yes, jwz doesn't have any issue with Emacs. But Mac used to use the same key bindings typical of Emacs, so jwz is miffed because for people comfortable in that environment, it's a pain to not be able to use the same shortcut for what amounts to copy, paste and cut.
I think he basically wants the kill buffer to be wiped out when you move between kills. His demo shows that in OSX text fields this is no longer the case, and at least on my machine running 10.6.something this is true. Emacs of course still behaves the way he wants.