Shameless plug - my app, Writing Streak, has the "typewriter" mode (Alt+T) that prevents you from editing the text you wrote, and a "blurred" mode (Alt+B) that hides the text you type, achieving the same effect:
I like the blur, but I find it hard to use. I make extremely many typos and my normal typing method involves simply hitting backspace a lot of times. Obviously I should address that instead of complaining about your blur feature on HN, but the gist is: if I can't even see the last few words I wrote, I'll end up writing gibberish :-)
If there'd be a "blur everything except the last 15 characters or so" kind of mode, or something where it gradually blurs characters as they're further away from the cursor (like a warcraft "fog of war" for typing), then that'd be ultra neat.
That said: WOW that app is nice. You got yourself a new user. I love how it's essentially device local and signup is optional. Super user friendly that way, in a literal sense (i.e. it's very kind & friendly to the user)
Blurring everything makes it impossible to fix (or see) typos which is annoying, knowing that the output of the thing is going to be full of typos. Hiding texts has another issue (even if not hiding the current line), that is you don't even have a rough idea of how much you've written and what the paragraph lengths look like so far.
If we do blur, but don't blur the current line, it solves both problems for me.
Does it support overstriking? Typing o<BS>/ is a legitimately good way to type ø, for example; it isn't a universal input method by any stretch but when it works, it's very mnemonic.
Just FYI, in "typewriter" mode, you can still delete if you use Ctrl + Delete or Option + Delete on a Mac. And then if you delete everything in "typewriter" mode using either of those key modifiers, using the other modifier on the empty text input crashes the app.