Back when Bluesky was in invite-only mode and I was giving out invite codes on Twitter, it used to be possible to just copy-paste the invite code into a DM with a rando and have them join.

At some point, that stopped working. Your account would get blocked and you'd need to solve one of those annoying CAPTCHAs. Following this change, I started to just take screenshots of the invite codes as they were visible on the Bluesky website, so black text on a white background.

Then that stopped working too and resulted in the CAPTCHA block, so whenever I wanted to share a code, I'd take the screenshot and overlay a random game screenshot on top of it to make it no longer just black text on a white background. Thankfully they didn't manage to stop that before the invite system went away.