I would largely agree with the parent's suggestions. Having an option for just the character would be especially huge, because as a native English speaker it's easy to think of the character as just a visual aid, and as such it's easily ignored.

Since you are in beta, I would find it helpful if there was a "report bugs" feature. For example, sometimes I noticed I would have something typed in correctly, but the application didn't recognize the tone marks I had (correctly) entered, which causes me to second guess myself. Or the voice recognition having trouble with certain words. I probably tried to pronounce the word for ten at least a hundred times unsuccessfully. I would expect to work at least once by accident. It would be great if I could just report this from within the app.

Other than that, I think the interface is great, and it's really FUN to use. Great job so far.