Viewers and Suggesters in a discussion may request Writer permissions (see Participant Roles and Permissions). To request Writer permissions, open the Discussion Menu and select Request Writer Rights. Optionally, provide a reason for requesting Writer rights. If you do not have Viewer permissions when attempting to access a discussion, you can request Writer permissions.
Only discussion Admins and Owners can approve users’ Writer permission requests. While Writer permission requests are enabled by default, Admins and Owners can choose to turn them off - to do so, open the Discussion Menu, select Discussion Settings, and uncheck 'Allow participation requests'.