The Mahara assignment submission plugin is being redeveloped from a basic summative assessment tool to integrate into the more sophisticated Moodle 2.5 assignment type. Initial work done by Ruslan (see the conversation here) has been continued by the community, and now Catalyst are working on finalising Ruslan's update to the plugin to work with collections and some other Moodle 2 functionality.
This development is very important, as prior to this only summative assessment of a portfolio via moodle was possible, i.e. submitted pages were locked (non-editable). Drafting was not possible, and attachments could not be submitted along with the portfolio. (Yes it is possible for students to share portfolios within Mahara with teachers but this adds more steps and complexity.) In the future self assessment and drafting will be supported within the assignment tool and gradebook functions in Moodle. Especially for new users this helps to reduce the amount of Mahara training, and given we are launching a common first year unit this year with 1000+ new users, in addition to new users from other courses, this is a big deal for us.
Update: I've been trying to find a paper on this, but a colleague +Danny Munnerley here who's teaching experience began in the UK, told me how the rubrics they used had a 3 stage reflective/feedback system. The rubric would contain criteria as usual, and also include 3 columns to the right. In the first column the student would self reflect on their performance for each criteria, the rubric is then submitted. In the second comment column the teacher provides their comment in reply. Finally the rubric is sent back to the student where they can respond to the teacher on their comments.