Well, that is exactly my point. Contrary to other demons who pretended to be Satan, Loki never presented himself as such. He was called like that by demons and more remarkable gods. So I thought that there was a concensous about who Satan was among those factions, some parts of hell and Olympus. In fact, it is told in those issues that Loki was banished to the underworld by the Olympians where he reigned. (I know, the first time I read it I thought the writers were doing a remix of three mythologies).
As you wrote, Loki isn't in charge of any part of Hell in the present, just as Mephisto described Satan, nobody have seen him in milenia and so his rule over Hell is in question.