ALL 3 input method keyboards can do copy/paste of any chunk of a message. It will copy from a text message into an email, but it won't copy/paste from an email to another email or text....
... example: view a recent text. Touch the message to get cursor to one end of the text block you want to copy. Press and hold the message window - a menu pops up offering option like, select text, delete, copy, paste, etc. Choose 'select text', then re-touch message to place cursor at the other end of the text block to be copied: it will blue-highlight the selected text. Press and hold the message window, select 'Copy'. Now navigate to another received (or new) text message, or to an outgoing email, press and hold message window, and select 'paste' and voila! In it goes.
It's a bit clumsy having so many steps, but it works - and for all three keyboard types!