I would love this personally. I broke my hand last year and while the apple dictation works pretty well I would have liked to have been able to do it directly in discourse too. That said personally I tend to waffle when I dictate! 
I also would like this for my family forum where among other things we share and talk about photos. Being able to record a message so the voice is captured and then to see that transcribed would be absolute gold.
Thanks for posting the request so succinctly.