Copy and paste into comment box?

Is there any way to copy and paste text into the comment box?
When I try to, it doesn’t work for me.

Yes, this is possible by double-clicking into the comment (you should see the insertion point blinking in the text, indicating it’s ready to edit) and using either the Ctrl+V shortcut or the Paste button if you have added it to the format bar. Later it should be possible to do this via the context menu as well, but for now either of the above will work.