[PShabi]

Sites do not advocate using other people's accounts for deceptive purposes.

They allow you to use all of the add-on programs you mentioned. They don't care if you bullshit about your hand in the chat box. Check/raising (perhaps the most absurd comparison of them all) is well within the rules of poker. Game/seat selection is practiced even in live casinos by regular players and is perfectly fine. The "heads-up" challenge question doesn't even warrant a response.

All of the things you mention are "strategic" in nature. I agree, playing under someone else's account is too, but sites do not advocate it. Stars will not allow you to change your screenname just because you want to. Email them and try it. Party Poker allows it once every 6th months. Not sure about the other sites but I'm going to be shooting some emails off here in a second.