As a Commenter in Air you cannot create share links. Commenters can use existing links they have access to, but workspace membership does not let them browse other people’s Showcases. A shared public Showcase link can be viewed regardless of workspace role. See Explore Showcases for the internal visibility rules. If a Commenter tries to generate a new share link, they’ll see a message like “No shareable link” or “You do not have permissions to create this link.”
Need to generate your own links? Reach out to any admin or editor on your workspace and request that your role be updated to Editor or Admin.