I have created a Public Community and I have invited people who tell me that they joined and when I check the members, they haven't.

This is because there is no button that says JOIN like on FB for a group.

What happens is that people follow the link and the screen they see is

Write Something

They assume that they have joined the community, but they haven’t.

If they don’t write something, which many people don’t have as they just want to join first, then they don’t join the community.

This is urgent.

Because now I have to explain the process to people who want to join, to have to write something before they will be able to log in or sign up.