The only things I don't like is the way you keep the misspelled words.
Most of mine are do to not being a good typist. actually I am a very bad typist and am used to mistyping letters I.E. hitting the key next to the letter I needed.
As such these errors make me look worse than I really am, since I double check my words. On the other hand your algorithm helps since it is fast, and always correct.
Also your compilation (your individual rating list) of my input does not seem to take in account of the individual comments, but keeps a running total of errors on my part. I would be better informed if each progress report was independent of previous reports. This would show me if I am improving myself.
A question, why do some comments using Disqus use Grammarly and others not. Case in point, this is being typed (using Fire Fox) in your review dialog box, yet does not use Grammarly.
I highly recommend this program, though not perfect it (this version at least) is close.