And it probably serves as a deterrent.
Precisely, and I don’t necessarily think that is a positive thing. I can understand if Lemmy servers don’t have the system resources to maintain a large simultaneous userbase as a reason to keep them invite only, since unlike something like Reddit it’s decentralized, and therefore many servers would not be able to afford sufficient hosting to accommodate such a large userbase, at least initially.
However, if the Lemmy network’s goal is to grow quickly and gain adoption, putting an artificial impediment in front of users wanting to register seems counter to that goal.
I’m saying there should be an box/non-clickable banner on this page on the opposite side of the box from the join button which indicates whether a server has open registration or not. Just a simple visual tag, nothing complex.