What if I just read about Bitcoin, found the forum through Google and want to get some help?
That's not going to happen.
I have to admit that it was one of the possible issue that I failed to be certain what the best solution is, but if I may assume, they can get from their crypto friend? I mean, someone should know someone else that's already on crypto, right? I never get any private torrent invitation code --and I rarely try to get any-- so I'm not sure how they worked, but isn't it work by having a friend that's already inside?
And about users inviting their alt, it's actually one of the purpose in my concept. With the tracking feature (in assumption that it is possible), we can track whose alt is who, thus when we get one of their alt spamming, we can track their account source (in other word, who invite them) and distribute the same consequences of banning (or negative trusts) to the inviter.
Regarding just found about bitcoin on google, I have to admit that I base the concept on an assumption that most --if not all-- people do what I did on my first time knowing crypto or when I stumbled on any website's membership; that is: reading and surfing around this forum a bit to know more before I decide if it worth signing up or not, which this forum faciliate by guest-mode. By the time they decide if they want to be on the forum, they have a slightly better understanding about crypto to decide if they're interested (thus, will make effort on being on the forum by looking for invitation code) or just sated as a guest that can only read and not post.
And about invite-source, the concept on my head was actually more to:
Suppose A is the guest, B is his friend who runs out of invitation code, and C is the invite-source. A will ask B, but as B can't provide that, B will ask C to give one. Which C will then inspect B's post history to see how related he is to spamming activity (thus, can roughly estimate how likely A is a spammer) and decide if he worth given one invitation code.
I would understand and withdraw the idea if this feature is not possible, though.