If the user selects something that is read only, and it is "copyable", should the application still copy to the clipboard if the users attempts to cut, or should it do nothing?
My instinct is that it should copy to the clipboard, but I don't know if that's going to confuse the user by implying that the data is editable.
On the other hand, if I were to compose a hypothetical context menu to "cut/copy/paste", I would think that read only data should not have the option of "cut", since that would be obviously misleading; so if the context menu item is disabled, it wouldn't make sense to have the keyboard (or other method) "cut" function as expected.