There is a thing known as a
TiddlyWiki, and there is a website that hosts them, known as
Tiddlyspot.
Nabble's embed forum functionality doesn't work with those, for some reason. I would like to request the additional feature of having this work, if at all possible (even if Nabble has to make their own TiddlyWiki designed for it—it's released under a BSD open source license, and so this shouldn't cause legal issues). I know, I know, you might not want to do that, but I figured I'd request it at least. It might be pretty easy to do, though.
I think I know why it doesn't work:
In TiddlyWikis, information is displayed on tiddlers, and thus the resizing of the forum might conflict with the resizing of the tiddlers. It might have something to do with how TiddlyWiki's are technically a single HTML file, and thus they are loaded all at once.