This is only a proposal but:
1/ it the sysmetric of the Unmount entry in the context menu of mounted devices
2/ I have to admit it took me a very long time to discover (by accident) that you can just (left-)click on a unmounted device to get it mounted automatically. I might not be the only feeling that you should be able to mount a device from the context menu ...
Twin of D15988 in Kio while dolphin is not based on the kio code for Places.