There are for sure smarter solutions, but one way to deal with the thread being locked is the following: Just copy + paste the post / text that you wan't to quote into the following snippet where the three dots are, insert the poster's name instead of your name, and finally replace the round brackets ( ) used here with angled brackets [ ]. It won't have a reference to the thread, though. But maybe that's not what is the most important to you.
(quote author=Texas_Tone)
...
(/quote)