There was a bunch of a hullabaloo about long-term sat accounts some months ago. The devs were going to put in some time limitations to prevent the sort of abuse that you are describing. However, the plan was not implemented. My understanding is that it's still on the "to-do" list somewhere.
In the meantime, it is not against game rules to have two accounts and also to perma-sit two accounts on each of those accounts, resulting in de facto control of six accounts. Reaction of players to this behavior tends to be negative, however; there are players who were attacked over perceived abuse of account sitting, although the results of that effort are ambiguous at best.
So: It's not against the rules and the devs won't do anything. If there are enough players who object and can identify a culprit, they could potentially do something. Speaking from experience, short of an open admission from someone who is also violating other community norms, probably people won't do anything unless or until they are directly affected, and possibly not even then.
If the tone of this post seems a little cynical, please forgive me. I find the issue to be frustrating.