[eluser]Unknown[/eluser]
I discovered the answer shortly after posting. This situation is caused by 'ShareThis', not Codeiginter. When you use ShareThis, take a look at the ShareThis code and you should see:
doNotHash: false, doNotCopy: false, hashAddressBar: true
Change this code to:
doNotHash: true, doNotCopy: false, hashAddressBar: true
and the sthash url component goes away.