You make a wonderful point. As someone who has staffed and/or moderated a number of popular forums before (including one with several hundred active members), it's very important to maintain an active and visible presence on the site you're overseeing. As demonstrated by the EU CMs, this means posting frequently and having disciplinary actions be visible - as opposed to deleting threads and having no trace remain.

This accomplishes two things. One, it demonstrates that staff is active on the forums and are probably reading everything you do. Lurking in the background and performing their duties without definite evidence leaves people with the impression that no one cares or is doing his job. Second, it establishes through repeated incidents a standard of what is acceptable content and what is not. This helps to not only allow people to learn what is likely to receive negative reactions by moderators, but it also ensures that staff maintains consistent standards because past examples can be easily, quickly, and clearly located for comparision.