When I double click a layer's name I can edit the layer name. I can copy the layer name, and past it back into the same field. When I press enter, and try to edit the name again it doesn't do anything. I cannot paste it at other layer's names either. The clipboard is loaded with the text, as I can paste it into other applications.
I remember this being possible some time ago. I have no idea if there's anything that I've changed.