The inability to append a collaborator tag to an Instagram post once it has been published is a constraint implemented by the platform. This limitation means users must designate collaborators during the initial post creation process; subsequent additions are not permitted via editing or other means.
This operational design likely serves to maintain the integrity of engagement metrics and prevent potential misuse of the collaboration feature. Allowing post-publication collaborator additions could skew data and potentially facilitate deceptive promotional practices. The initial design choices reflect Instagram’s ongoing efforts to ensure authenticity and transparency within its user interactions and advertising ecosystem.