So I guess we should follow the local law and only share with close family? I think in my country it means people sharing in the same household. But then they could just come and play on my computer; so sending a copy of a game is actually more useful for relatives not living in the same place, which would then be illegal?
But there is the law and there is what developers would actually rather not you do, which I guess is sharing with complete strangers (or a family/friend circle a bit too big).
If the files are sent directly to other people or uploaded to some other server, there is no direct way to track them. But if an account is shared with numerous people, itch.io may be able to detect too many simultaneous connections, from too many countries (you could tunnel to mitigate that, but probably still get different regions/IPs). No idea if they do, though.