Snapshot 13w09c, Snapshot 13w10a
Windows 7 Professional 64-bit, Java(TM) 7 update 5 (64-bit)
See images for details of the bug, I thought it best to show pictures because it is simpler to understand.
Sorry my bad English, I tried to put in a way that gives understanding.
P.s.: I'm from Brazil.
MC-8826 Adding an item to a hopper with a dropper does not change comparator state.