This is accurate -- it is definitely a draw for Organized Play campaigns that characters be portable, and I'm not trying to say that it isn't a draw.
However, there have always been limitations on character portability -- adventure tiers prevent high level characters from showing up at low-level tables, for example. Likewise, there have generally been a few story-based reasons for characters to lose portability -- in Living Forgotten Realms, for example, a character could gain a story award that removed them from play until another character belonging to the same player played through the next adventure in the series to 'rescue' the character with the story award.
The Demiplane of Dread award falls into this latter category -- a story-based restriction that enforces an aspect of an adventure season. Without it, later runs of Season 4 adventures simply won't feel like they're taking place in Ravenloft, but rather just another part of the Forgotten Realms, and a good part of what makes Season 4 interesting and special will be lost. I don't feel that character portability is such an important part of the Organized Play experience that this kind of story-based restriction should be tossed away so cavalierly, especially when there are other, non-story based reasons for the restriction to remain in place.
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Pauper