I think Dan misunderstood the original report when he said this was fixed.
Our PM system is different from vBulletin's, in that PMs are threaded. When you click "Reply", you're replying to the thread (and its recipients), not to any single user. This allows for easy group conversation. This was by design, and based on the design of the PM system of a major website that also has threaded PMs. It's not intuitive to have PM threads with varying recipient lists.
That being said, I mentioned your confusion to Ted (who handled all of the PM UI), and in the interest of preventing further confusion, he's going to make the recipient list on the PM reply popup editable. If you leave the recipient list unaltered, your reply will go to the thread; if you alter the list of recipients, a new thread will be created. Hopefully this will result in fewer misdirected messages.
Until we're able to make that change public, whenever you want to reply to a list of people different than the list of recipients of the current PM thread, please return to your inbox and initiate a new PM thread there.
Edited by frankfarmer - Fri, 06 Feb 09 03:30:10 GMT