I don't kno wif this feature is working in 1.3 but one thing very
important in my opinion is the fact that several person may be able to
modify the same page, for example saving only the paragraph modified.
It's not working in the 1.2 and thus it's a shame because you can't
work in a medium sized page within a group.

No, it does not work yet. Actually this is part of the work on the new version of the WYSIWYG editor. We are currently working on trying to make real-time edition by several people working in the editor's next version, but it will most probably take a few months before it becomes available.

You can follow the discussion about the WYSIWYG editor here : http://dev.xwiki.org/xwiki/bin /view/Design/NewWysiwygEditorBa sedOnGwt

Thanks,

Guillaume