Well if your intent is negative and you trying to beat any security measures by asking this question the bottom line is that all your activities is known to the administrator and once you go wrong it can be seen.
If you are clean you need not worry if you your editing is seen by administrator or any member for that matter stick to the forum rules and you would be good to go
i ask this, becouse now i see so many user, baned for plagiarism.
and if admin cant see edited history, this is mistake, becouse if i make post, and if i want ban users (for example high ranked users - for earn more money with bounty signature) i can edited my post, and make similar with another user, and if my post will first. admin can delete others. this is bad way. and i think this problem will come, if admins cant check edited history.