copying text from song comments is not really working with latest Renoise on Linux (Debian stable/testing + Awesome window manager in my case).
It just doesn't work, selecting text and pressing CTRL+C, or selecting copy from the menu, seems to have no effect, the clipboard stays empty.
Pasting works only sometimes, when you copy something, e.g. from Firefox and try to paste it into song comments results in an old clipboard being pasted most of the time. In rare occasions it works when closing and opening the song comments window.
Please let me know if you need more info.