Selecting text from comments in Youtube pages on Firefox for Android does not work

On a Samsung Galaxy Note 10.1 (not 2014 version), run Firefox for Android. Navigate to

http://ift.tt/1ARfY1x

Scroll down the page until you see some comment text. Then use the stylus to select some text. You can't. I expected to hold down the stylus on a word and see the highlighting markers there, but nothing happens.

This works under the stock browser on this tablet.

Is this more likely to be a bug in Firefox for Android or a tablet firmware issue? The answer will give me guidance as to which party to file this to next.