This may not technically be a bug, but it violated my expectations:

setup:

      (setq org-capture-templates
	    '(("t" "task" entry
	       (file+headline "notes.org" "Refile")
	       "* TODO %?\n  %U\n")))

Use 'C-c r' to start capturing.

Type 'foo'.

C-c C-w to start refiling

Type 'bar'.

Decide that you really didn't finish the note, and type C-g to get back
to editing the note.

Notice that your typed-in text is vanished.

C-h l output of a test case that shows this problem:

  C-c r f o o C-c C-w b a r C-g