I haven't experienced the behavior described but reading it, I instantly hate it. It would differ from every other program I use.

I'd counter with there should be two different paste actions in every program: plain and smart. I almost always don't want to preserve rich formatting when I paste text. It looks like my cat walked over the keyboard while I was typing. The action to paste as plain text versus a fancier/DWIMy method is often different from program to program.