I just used it. I clicked the "+Quote" button in the bottom right of your post. Then I clicked "Insert quotes..." in the bottom left of my post (next to "Attached files" button). Then it brought up a pop-up box that asked me which quotes I wanted to include. Drag and drop or just click the "Quote Messages" button in the bottom right and your done.
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Aw, man, did that work! Tested it in this thread, and pulled up 30 or more quotes from all the times I tried to use it over the least season and this offseason.
I was using a workaround, where I had two tabs opened side by side with the same page of the same thread. In the left tab, I had an open reply box. In the right tab, I would type replies to various posts, one a time, then cut each reply and the quote and paste it into the reply box in the left hand tab.
Once I had it down, it went a lot more quickly and easily than it sounds. But still, the normal way is preferable, so... thank you!