WTH, a 302 into a "mailto:" (search for "HTTP redirect" in the featured article) opens up my e-mail client without clicking a mailto link!? This seems wrong.

Some browsers ask whether to open the email client in that case. I don’t see it as significantly different from a redirected download link that would open a program based on the mime type or file ending. Or from a redirect to another URL pattern associated with an app, like for example how YouTube links may open in the YouTube app.