Highlight a section of the text in the readonly textarea, and either hit Ctl-V or right click on the selected text and select paste. The text in the clipboard is pasted into the textarea in place of the selected text.
confirming. using the 2000081404 nightly on win2k
assigning to kin, kin i believe you already have one that is similar
*** This bug has been marked as a duplicate of 45645 ***