Typically when I have to paste formatted text within a rich text box of a web app, I paste it into the search box of the browser first to remove the formatting & then paste the un-formatted text in a rich text editor. What a pain!
I learnt from the WebApps StackExchange forum that in Chrome, you can use the keyboard shortcut Ctrl + Shift + V to paste the unformatted version of the copied text.
While monkeying around to see if there is any trick to make this work in browsers other than Chrome, I serendipitously discovered that Ctrl + Shift +C opens Developer Tools in Chrome & triggers the Inspect element hotkey that shows a tooltip for a webpage element that you hover upon.
Also see:
Keyboard shortcuts common to Firefox & IE