Are you saying that the tabbed characters don't appear in the characters list of worlds - are you trying to sort them into a Worlds folder?
We ran a few tests; the tabbed characters must be added through "Submit Character" and appear when posting IC, but not in the general characters list. Which makes sense, considering that tabs are not technically their own character - they're more sub-characters. It's the same concept as why you can't sort tabs into their own folders on your main character list. It's not so much a bug (we think) as it is the nature of what tabs are. Worlds use similar framework to the rest of the site, including the characters list, so since tabs don't show up on the main character list, they won't show up in the Worlds'.
It would be nice to have the functionality to sort them in worlds, though. ^^