annotations / comments for web form / wysiwyg editor

I am building a web application where users can write articles. It's written in PHP / mySQL.

At the moment I use a simple text form where the users can write their content. Formatting is done later by XML export / Layout application.

BUT: The users would like to share comments for eachother. To understand: Microsoft Word has a nice commenting feature. There is speach-bubble with a comment from every user. At the moment the users write their content in Word documents and send those by email to eachother.

Now: Does anyone knows a solution for comments/annotations in WYSIWYG editors like "MarkItUp!" or TinyMCE. I do not use any WYSIWIG at the moment, so I could implement any of them. Or some other way to do this...

One idea was to implement a comment function just as an additional text box - but that would not allow to make comments for individual words/sentences.

I've found http://www.youtube.com/watch?v=WzaCj6KGvWs, but I cannot find the plugin for download.

Thanks a lot for any ideas. Silvan

This is what you are looking for: http://nytimes.github.io/ice/demo/