I'm running as a limited user, I have done so since XP, and still don't have any issues with copy/paste. I also don't have any issues copy/pasting between regular and elevated processes (there are no security restrictions on that, I think lensman is confused with drag/drop between processes of different accounts or integrity levels which is restricted).
You still haven't described what your problem actually is, other than "it's broken". Can you give a concrete example with repro steps of something that doesn't work?
I do also experience this issue in notepad where it is almost impossible to target............http://channel9.msdn.com/Forums/Coffeehouse/Windows-8-Copy--Paste-bug
I'm not sure I understand this... Are you using a mouse or touch?