Ok so placing []'s in the ID attribute is not too smart, as its non compliant.
SO . or _ should be used instead.

This goes for normal article id tags, which would hinder custom css skinning.

I found the editor would only load on the static page content text area and not the pre-content.
Also any changes were not saved properly.

I dug around and found its a problem with the way TinyMCE is configured in its plugin, it looks for fields with the id of serendipity[plugin][content] and ...