It's not the best solution, but usually I just keep a notepad document open on the side. Click and drag through an RP response, crtl+c, then crtl+v into the notepad so I can freely look back to it as needed.

Fighting with the chat scroll in crowded areas is too much of a nightmare otherwise, and it helps me keep everything organized and saved for archival purposes. Also lets me freely type out and see the entirety of my post before I post it, which can help me a lot personally since I lose track otherwise, or if I want to rewrite something before posting it, I don't have to fight with the text box.