I've taken to paste everything in kate or notepad first, then recopying it and dropping it to the final destination. Happy to hear a big software package moving to better defaults. Hopefully a lot of others follow their example.
One trick I've found in Word specifically: press Ctrl+v to paste, then hit Ctrl, then hit 't' -- this is the key sequence for paste->open paste options->use plaintext.<p>You can do the same thing by pasting, then click on the little box that pops up next to your pasted text, then clicking the text option.