Basically, you can let people know however you want... as long as it's not spam.
Referral links still work. The promo codes are just there if you want to pass some of your referral fee onto the person signing up.
Yeah, those are just clicks, whether they signed up or not.
I'd just add that even if you offer a promo code, you should probably still use your referral link. That way, if they forget to enter the code, you still get your referral fee.
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