Allow opening up a team so people can join without invites
In open source projects (like those run by Wikimedia!) it is important that everyone be able to join openly without needing an explicit invite. Having some support for this would be great and also definitely help stem some of the flow from IRC to Slack, redirecting it to mattermost instead.
There is a setting for this under Team Settings → General → Allow anyone to sign-up from login page in Mattermost v1.2 and up.
Setting it to “yes” will add a sign up link to the login page, so anyone is able to create an account.