org-capture-kill (C-c C-k) used to abort capturing puts the contents of the capture buffer into the kill ring.
This is obstructive when the user wants to abort a capture, but save a portion of the text into the kill ring to yank elsewhere. The aborted capture contents will replace the desired content. Aborting capture should act transparently like killing a buffer. It shouldn't affect the kill ring. If the user wants to keep the capture contents, he can trivially run C-x h mark-whole-buffer M-w kill-ring-save
