I think it is a natural fact that mods are held to a different (not necessarily higher) standard than members. Since not every member would be selected for a moderator position, there is some standard by which they have been distinguished from the general member base.
However, this does not imply that their posting must always be exemplary. As PizzaPlanet said, what defines their competence as moderators is their moderation, not their posting. Furthermore, all of us are human and are prone to making mistakes. What is important is that moderators understand the rules, try their best to follow them, and set a good example for others. This is simply a case of them adhering to the standard that is expected of all posters, and will be easier to measure once we have rules.
I also want to clarify the purpose of the Manifesto. The Manifesto governs administration and moderation, not posting; the rules (when they are formalised) will govern posting. In this sense, the moderators are to be held to the same standard (defined by the rules) as everyone else when posting, but to a different standard (defined by the Manifesto) when moderating.
This will all be simpler and easier once we have rules. Please sit tight until then.