Found on the github -> please test on your site worked on mine.
Change your TPL: QuipReply.tplAddComment
Look for submit button:
Find: <button type="submit" name="quip-preview" value="1">[[%quip.preview]]</button>
Change to: <button type="submit" name="quip-post" value="1">[[%quip.post]]</button>
Hope it works for you.