At the very least if you're going to delete someone's post then you should PM them to let them know what you're doing.Things like this really just annoy people.
That is all I wish to say on the matter. It is clear, concise and comprehensive. As any good report should be.
This then immediatley means you are engaging that person via the PM system if they have any complaints so you won't have to hide behind some rule for your ruling. You will actually have to explain yourself. Also they (the "off-topic" poster) will be less inclined to start a thread about it. Just makes sense to me, if you don't want people "questioning admin/mod actions in public" then fecking engage them in debate before they do.
Also, if their off-topic conduct becomes a problem then you will have given them ample chance by warning them via this system.
And stop deleting Withcheese's posts on the sly, I hear he's getting fed up of it.