I was disappointed to discover that the item duplication bug was not fixed in this re-release. Otherwise, I'm loving it :)
Does anyone have any info on why this flaw wasn't fixed?

Didnt even know this flaw existed.
Likely reason it wasn't fixed is that it wasnt priority - heck, the only reason the game got attention w/ the updated res patch is because of Diviinty 2 coming out.

I wasn't aware of it either. Is it something that can screw up your game, or can you just ignore it and not use it?

You can ignore it completely.