There are still some thing that this trick could not actually do. Based on your tutorial, in order to quote a locked topic you should copy and paste its contents then what you will only got is the plain text of the locked thread. You won't be able to quote it's image, text format (Bold, Italic, underline, strike through, color, font style and font size), text alignments (center, left,), table, list, horizontal line, quoted reply, and text with links unless you do it manually which will take some time.