The hilarious thing is that the "geas" concept is in no way original to Code Geass. Its a very old magical concept intertwined with the "evil eye". But this is typical of people who are "bright new and shiny" - they don't realize that ideas were around and things happened before they started paying attention
I get the impression the CG fans saw her eye and just automatically made the assumption it was a reference to CG or a borrowing from CG -- whereas it doesn't seem to have a blooming thing to do with CG.