Good job first of all.. So out of fun, I typed in "the dudes and dudettes were here" to test your system. The neutral responses as rewrites were a bit worrying. You may want to look into it. Congrats on it. EDIT: @Mikkiq, thank you for taking those words out promptly and correcting it. Cool site.
Not sure if it was another word, but the word 'dudes' still has a suggestion to a word I'd firmly rank 'impolite' when I tried just now. That said it includes a whole bunch of swear words (marked impolite) - I could weirdly see using this to add a bit of flair to a put down.
I do find these things quite fun; I put in "You are a sexy beast" and got "You are a hot dog" as neutral, "You are a beautiful dog" as neutral but "You are a beautiful horse" would be pushing it and impolite; though "You are a glamorous horse" (or hot) is neutral.
Giving it a go with some Donald Trump twitter text, the suggestion was "President Obama was terrible on @60Minutes tonight" is impolite; a suggested change that would be more polite was "President obama was incredible on@60minutes last night.". I noticed with that it looped through the same words a few times - in some cases labelling the same phrase as both neutral and polite.