I thought you were a normal user, and a mod was telling you this, in which case the only way for a non-staff user to edit the guidelines might be to move it.
In case you are a staff member expecting all staff members the ability to edit the guidelines, that is reasonable and how it works. Perhaps there is a bug, or perhaps a different setting at work (such as edit timeouts; I don’t have mods, I don’t know how their “powers” work, per se).
I would expect admins and mods to be able to edit the document.