Naven
Glossary
Public channel
A space anybody can find and join without being invited.
Discoverability is the point and the problem. Public spaces grow without anybody's effort, and they attract people whose interest in a space full of young strangers is not the stated topic. Every platform that has run large public communities has had to build moderation for this specifically.
The alternative — no public discovery at all — trades growth for a much smaller attack surface.
Where Naven stands
Naven has no browsable directory of channels or of people. A channel is reached by a link somebody sent, which is a deliberate limit on growth.