I wonder who that someone is!

I'd say it's just common sense. If you post a post containing something filtered/forbidden, deleting it wouldn't have much use if you were allowed to repeat it. The admins know what was in it (we can view deleted messages and if the offense was edited out we can ask the one who edited it out), so there is no need to state the exact contents of the post in public anyway. You can just use the name of the offense, for example "bob's personal attack" or "archibald's flame tag" or whatever.

Also, if something was edited out, it was obviously not in accordance with the rules for post content you linked to, so repeating it would automatically make the post it's repeated in not in accordance with the rules too