I've been trying out XenForo using the demo facility. I've noticed that moderators are able to moderate posts written by administrators (by default). What needs to done to restrict a moderator's ability to moderate admin posts (without restricting their ability to moderate all other user types)?
Give the moderators the ability to soft delete posts but not hard delete. If they moderate an admin post then undelete the post (as an admin) and then have a word with them about why they felt the need to moderate an administrator post. Also ensure they know who are administrators and that they are not to moderate posts made by those users under any circumstance.
It's not a simple "tweak", but I am looking into this with a few people. Don't expect me personally to release something. This particular tweak is over my head to realize. No promises, but .. hope to give you some good news soon.
Not all who engage in fora are well-intentioned, like-minded chaps who would never post maliciously. I don't want to be in a position whereby a disgruntled mod could potentially take umbrage and start deleting admin posts.