Not very difficult if you have an online presence somewhere you can use as proof that you will act in good-faith. Having a hacker news account for instance can make joining as easy as sending someone an e-mail (as I did) and asking. It is a website much more built upon trust, and so if you invite someone and they get banned for something, you are directly connected to that.

For more see: https://lobste.rs/about#invitations and the user invite tree https://lobste.rs/users