To be honest, I don’t think this “I like to select text as I read” behavior is compatible with select to quote, which is why this option exists and has since just after we launched Discourse in Feb 2013:
Other
Enable quote reply for highlighted text
I suggest turning that off …
You can always highlight then press literally any reply button, e.g. the one at the bottom of each post, the one at the bottom of the topic, the reply as new topic in the guttter – and this will generate a quote. Try it.
There’s also the first toolbar button which is a quote everything button.
p.s. all this 
was discussed to death back in 2013, believe me