Dust2Dust, any instance of Sitting Abuse on .net is, as far as I know, dealt with by the more senior moderators ingame, and they are dealt with on a case-by-case basis. Action is only taken (again, as far as I know) If there is substantial proof that either a) the sitter caused great damage to the account or b) through intentional inaction, let great damage be done to the account (i.e., taking the sit, knowing that it had a lot of attacks incoming, and intentionally leaving troops to be destroyed or letting villages be taken, though such a case would have to have strong evidence that it was malicious rather than just negligence (Mails, etc.)).
Lunafire, while I agree that sitting abuse is bad to see, I honestly don't think that this will make any difference. No matter what level of permission they have, a player can still abuse a sitting:
If they can move troops, they can support their allies with its troops and destroy the offence of another tribemember, or they can attack another tribemember with the account's offence.
What about a situation by which there is a spy in the tribe, and they want to let someone else sit the account and see the forums. As it stands, a leader can instantly see someone outside the tribe is sitting, and kick the person as a spy, but if the person tells the leader that they haven't given them forum access (when in fact they have) what can the leader do then? It would make it much easier for spies to work within tribes. Is it the fault of the leader that they have trusted a player that they didn't know would betray them? How then is that different to it being the fault of the sat player to have trusted someone else to sit them without abusing their account?
