1) I'm working on implementing Markdown and will be using friendly headings once we sort that out.
2) I love this idea! In fact, it's been on my wishlist for some time now -- I plan on shipping it this week. I've been calling it "Snapshot Backup", but I think "Archive" is a much better word for it. Thank you :)
Interesting, thanks for the feedback. I definitely plan on adding an off switch for Markdown, and will only be going through implementation if it doesn't impact speed/usability in a noticeable way. The plan is to make it a minimal implementation (i.e. keyboard shortcuts only) and barely something you would notice you had.
The reason I'd like to add it is because having switched over from TextEdit and Evernote, the one thing I miss are the Cmd+B,I,Us etc.
This may be a known issue: it has to do with the fact that whenever Dropbox syncs, the undo state is reset. If you haven't setup Dropbox sync and have been experiencing this, let me know.
Out of curiosity, which browser are you using? As far as I'm aware, I didn't build in any Cmd+N hijacking into the app (I did do Cmd+S for syncing/saving though, and Cmd+1,2,3,4,5 for switching between files -- is that what you mean?).