I am confused whom I should listen to. The offer is really tempting but I want to be sure it not a scam
You will get the 5% discount no matter what code you use. Search google you will find one instantly.
Don't click on the referral codes of people who SPAM - or else you just encourage such behaviour.
(P.S. 5% is a terrible offer anyway. Instead of having a 1% fee, you have a 0.95% fee. You are talking pennies.)