Wasn’t this “postcard-ware”? I seem to remember ADOM was postcard-ware at one point.
That could introduce a geographic bias.
That wouldn’t prevent someone from sending multiple cards from different locations with fake names on them, for instance. Even if XYZZY sent some kind of confirmation code to the return address, the person (or a friend of theirs whose address they used) could go there and get it.
I can play the games for free, while naked. Mailing a postcard requires 45¢* and putting on clothes. You’d be surprised how much resistance that generates.
*if I’m mailing something from within the US, and assuming the destination is in the US. It would cost more for anyone living outside of the US, of course, which is why “geographical discrimination” is a fair assessment.
Postal mail is hardish to send from here (Bénin - there is no such thing as a mailman; one has to go to the main post office) and tends not to arrive anyway. A main reasons for having a mail service at all is to be able to sell special edition stamps to collectors worldwide.