The raw protocol window/tab doesn't support clearing, like normal channel or server tabs. Edit -> Clear Window is displayed as enabled, but neither that nor Ctrl+L do anything.
Thank you for reporting this bug in KDE software. As it has been a while since this issue was reported, can we please ask you to see if you can reproduce the issue with a recent software version? If you can reproduce the issue, please change the status to "CONFIRMED" when replying. Thank you!
This is unchanged, although Edit -> Clear All does affect the raw tab.