The ability to include another user as a collaborator on an Instagram post, even after the initial publication, is a feature that expands the visibility and reach of content. For instance, if a photographer forgets to tag a model in the original post, they can retroactively add the model as a collaborator.
This functionality offers significant advantages, including shared engagement metrics, broader audience exposure, and streamlined content crediting. Historically, if a collaborator was missed initially, the post would either need to be deleted and re-uploaded or rely on a tag in the caption, both less effective than a direct collaboration. The availability of this editing option reduces the need for such disruptive measures, maintaining post integrity and engagement.