"right click -> Copy As PlainText"? Office 2010 still doesn't ship with such a feature, and it's been a problem from the '90s!"
Have you used Office 2010? There are multiple options to pasting: Keep source formatting, merge formatting, and keep text only. The options in Excel are even greater.
As crazygringo said, the problem is copying from Office into textboxes. Any developer who's ever worked on a web-based CMS will tell you how painful it is to have to deal with people pasting walls of text from Word.
(And btw, I do use Office 2010 every day of my cursed life...)
Have you used Office 2010? There are multiple options to pasting: Keep source formatting, merge formatting, and keep text only. The options in Excel are even greater.