Thanks @jasonsmith for the feedback, appreciate it
CTRL+SHIFT+UP is also an option, that's true. One worry I had is whether the extra "SHIFT" makes the shortcut less accessible (combination of three keys instead of two) given replying to a previous message is so common. But perhaps that's not such a big concern. At least it wouldn't conflict with CTRL+UP.
Out of curiosity, would you find reprinting previous messages useful?