Indicate when Ctrl+V cannot be executed (e.g. in read-only folder)
Use cases
I recently tried to Ctrl+V a file into a folder that was read-only without me knowing. Since there was no free space at the bottom of the file list to right click and see that the "Paste" entry is greyed out, I repeatedly hit Ctrl+V and wondered why the file wasn't being pasted. I suspected some focus/accelerator key issue until I tried to do it on the terminal and saw the "permission denied" error.
Desired behavior
Should Ctrl+V not succeed or not be available, a pop-over or something should inform me that my command was received but could not be completed because of reason X.
Benefits of the solution
I immediately know that something doesn't work.
Possible drawbacks
None that I can think of right now.