I appreciate your concern, but you can't fault JS for browser bugs or OS bugs.

It's also not clear to me why you're any more secure with a signed browser extension or native app. Just because it's signed doesn't mean you can trust it any more than you can trust JS that you download via HTTPS from a server. What's worse, you didn't compile it from source, so how can you know there's nothing sinister lurking in there?

You are correct that people like native apps for their microblogging, and we want to encourage many native, hardened, peer-reviewed implementations for every platform imaginable.

Because the client is just appending signed entries to the end of an RSS file, send pushing and pulling those files over http, you could write a nice client running inside emacs (if you trusted your os crypto libs).