Only question I have is about the content I write into your text box. Is it still mine? Is it private to everyone (even your servers)? Writing is a personal exercise and can be creatively rewarding, but only if you've got the confidence that it's still solely _your_ writing and that you control who can see it and when. The only privacy callout I see in your about section is regarding other users on the app not being able to see your content. A paragraph about what you do with the writing I put in your tool would help me not feel worried that I'm writing with someone over my shoulder who owns my words as I pen them.
Again, good work so far!