You can flag your post for moderator attention. More times than not, your reasoning will be justified and a moderator can remove the post for you. But removing the ability to delete an active post is a way to prevent people from inappropriately or maliciously removing content licensed under Creative Commons.
The ability to delete your post is available when it has little activity (upvotes, answers, etc) because deleting it will typically have no effect on other parts of the system.
But once people start adding to your post, it becomes part of a collection. The other answers, the voting, and the comments all work together to create a cohesive collection. Arbitrarily deleting a portion of that collection could materially harm the value of that material… which has already been published under a Creative Common license for reuse.
Also, you cannot arbitrarily terminate your Creative Commons license grant.
That's what "perpetual" stated below means; continuing forever or indefinitely.
- License Grant. Subject to the terms and conditions of this License, Licensor hereby grants You a worldwide, royalty-free, non-exclusive, perpetual (for the duration of the applicable copyright) license to exercise the rights in the Work as stated below:
Even under Section (7) Termination, it explicitly says that, even if the author chooses to stop distributing the work, it does not serve to withdraw this license.
Subject to the above terms and conditions, the license granted here is perpetual (for the duration of the applicable copyright in the Work). Notwithstanding the above, Licensor reserves the right to release the Work under different license terms or to stop distributing the Work at any time; provided, however that any such election will not serve to withdraw this License (or any other license that has been, or is required to be, granted under the terms of this License), and this License will continue in full force and effect unless terminated as stated above.
The usual "I am not a lawyer" disclaimers apply, but I have read that license agreement backwards and forwards and that's how I read it.
However, you can request to remove from the Collection any credit as required by attribution (Section 4(c)). We will do this on request, but the material is published as part of a collection and we feel that removal of that content would materially harm the collection licensed for reuse.