I know this is already in the works given discussions I have had with some of the devs, but currently the app does not support the ability to edit and delete posts within the app. One has to browse to the Kitsu website to make any changes.
Such a feature is necessary to have in the mobile app, especially for those who may prefer to use nothing but the app for their anime tracking and discussion needs.
Posting this as feedback so it can officially be marked as in progress so other users are aware it is in the works.