Too many dupe accounts, too many spam bots, advertising bots, paid post content accounts etc. Not even going to get started with the ever growing number of scammers just waiting to take advantage of unsuspecting members. And this was the issues when we closed/limited registrations almost 2 years ago.

Today we're at the dawn of AI. Before you know it, all of the above will be automated and indistinguishable to most anti-spam and anti-bot captcha challenges.

Selling your invite code is not illegal, but just remember that every code is tied back to the account which issued it. Once fully rolled out, you are essentially vouching for the person who you are bringing out of probation. Currently the person who invited is only visible to mods - but we might eventually open up the information to all members. This will not stop ALL the above issues, but it will make it much harder, while opening up the community for legitimate new members.