So it was sort-of-rumored , so shall it be. Valve's officially announced the second dollop of Portal 2 DLC (via Joystiq ), and it includes "an easy-to-use in-game map editor that will let users design, build and share their own single-player and co-op test chambers with the community." It's coming out early next year.
Beyond that, the only tidbit Valve's allowing to seep out - in much the same way one would utilize a deadly neurotoxin - is a vague mention of voting for your favorite levels. Community features, then, are probably a no-brainer - which is roughly the state one would find themselves in after being exposed to a deadly neurotoxin.
What about a GLaDOS-powered "spellcheck," though? Valve's said nothing, but fingers crossed, obviously. As a rule, Valve's notoriously tight-lipped, but I've asked for more details just in case.