And if you are chosen to share the collection with anyone at Lightroom.Adobe.com then all you have to do is send a link to whomever you want to view the collection.
I've done that, but it seems that you have to have an Adobe ID to make comments. My question is about people who DON'T have an Adobe ID.
That's right. This area is pretty new and has changed quickly, so I wouldn't be surprised if it changes to allow other ways of authenticating comments.
For now, you can always set up a dummy account and tell people to log in using that user name and password. If you need more than one person to view a set of images, just duplicate the collection and sync it too (this doesn't mean extra uploading). So, for example, client John might log in using mydummyadobeID and select from the Shoot-John collection, and client David would use the same ID to view the Shoot-David collection.