Double neutral wiring
It doesn't look like they shoved 2 ends under the screw - that would be very shoddy indeed.  It looks like they stripped insulation off about 1" of the wire mid-run, and looped it around the screw.  That's legit.  

If you need to cut that for some reason, either pigtail or cut it dead in the middle and get a "screw-and-clamp" type recep, which allows 2 wires per screw. Easy peasy.