I got aware of an interesting behaviour of STACK questions regarding the display of the standard feedback for correct/partially correct/wrong answers. I don't know whether this is intended or not but maybe it's helpful to know.
If you work with an HTML-editor (instead of plain-text) and if you cut the token "feedback:prt1" from the specific feedback and paste it to the question text, than an empty break ("<br>") might still be left in the field for the specific feedback.
If your question has more than one potential response tree than the standard feedback for correct/partially correct/wrong answers will be displayed both at the place of every feedback token and at the end of the question.
If you remove the break (or any character) from the field for the specific feedback than the standard feedback is only displayed at the places of the feedback tokens (as probably intended).
To empty the field for the specific feedback you might have to change your editor to plain text.