ChatLogger allows you to do that outside the game. I haven't updated it in a while, but it should still work.
I'm also currently working together with Baertram on updating pChat. I'm not 100% sure yet how we will handle the copy feature, as it relies on a part of pChat that we are trying to get rid off, but in some way or another the new version will be able to copy the filtered messages as you see them in the chat tabs.