Paste as Markdown is a browser extension to paste as Markdown. Watch it in action:
It lets you paste the content of the clipboard as Markdown, in any webpage, on any webform. The content of the clipboard is unmodified.
Yes. No data is sent outside of the browser, everything happens locally.
I'm sure you do! If so please leave a review on the extension page of the web store for your browser of choice. Thanks!
The site that let one copy and paste rich text as Markdown used deprecated technologies; it's been retired.