I definitely see what he's saying that makes it sound like a "k" sound (the voice software trying to parse the two words together into a seamless sentence where an artifical space makes the next sound sound like a different one) but there's not much that can probably be done about that. Plus, it still sounds like mostly and h to me (and the others here) :p
Yah, jinguist, I usually keep google translate open on my desktop so that I can check spelling if I have any doubt. That said, our Tireless Moderators are not the ones who have any power over this. It is Duolingo admins, I believe, who may respond to trouble calls/bug identification/new ideas.