Discussion diaries as a reflective assessment tool?

We use LiveText as our ePortoflio system here. It provides the ability to create an overarching portfolio as a means of demonstrating personal growth through the program. Each final portfolio requires a piece from each course that demonstrates an understanding of the material presented in the course. Currently, this is usually the major project and a reflection. I read something this morning about a webinar on discussion portfolios. This got me thinking about the purpose of the signature piece in an online course. Many courses have, being partially constructivist (and sometimes even constructionist I would argue) in nature, a high value on the discussion posts in any given course. Does it make sense then for the discussion, since it is weighted heavily and also represents (hopefully) the evolution of understanding by a student in a given course, to use the discussion in some form as the signature piece?

My thought would be to create a discussion diary (within LiveText or what have you) where students can post favorite discussion posts or threads and create reflections on these threads later in the course. Basically a kind of ongoing monologue on the posts they find important to themselves and what it comes to mean over the rest of the course. This could replace or augment the project as the demonstrative piece.

Then, over the course of the program, the diary could become part of the final portfolio, perhaps with an overarching reflection on the discussions themselves. This wouldn't diminish the need for a rubric for discussion performance, but perhaps could split it into two sections, the first a pure assessment of quantity with the discussions themselves, and the other rubric run against the diary as part of assessment at the end of the quarter.

One of the things I like best about this idea is that it would show growth over the course of the quarter better than the major project would, in that it is not a single research-based test point in the class, but more of a continuum over time, showing multiple points in the development of understanding of the topics presented . The rubric would be a real challenge to develop.