This is definitely an interesting discussion that has been ongoing in the Arab world education programs as well.
In Egypt, the program adopted a byte threshold/goal in most classes. Bytes do allow for quick, surface level evaluation to see how much students are contributing. Our ambassadors seem to appreciate having a benchmark for student contributions, but we have also gotten pushback from the Arabic Wikipedian community fearing that the primary focus is quantity, and not quality contributions (like Craig mentions). Most of our students in Egypt do translation assignments, so it is often more important to select high quality content in the other language, and ensure that students are not copying and pasting machine translations and wikifying their contributions. I've noticed students in Egypt like having a numeric goal more than their teachers do.
Here's an
example course page from an English translation class at Ain Shams University. You'll notice they set a 50kb threshold, and also have a section for additional contributions of 5kb each. (To compare these numbers to English/latin scripts, you should halve the bytes because of the Arabic script which "inflates" the number):
Like all assignment guidelines, having a byte benchmark might be a necessary evil, just like traditional writing assignments tend to have minimum word count or pages. Depends on your context and goals. It would depend on the rest of the assignment and the rubric you would use to evaluate the assignment. Giving more weight to proper writing style and citations would probably be a good place to start.
Juliana, it does sound like you want your students to contribute more since they're stopping when they reach the minimum. That sounds like normal student behavior. Would there be a different way to motivate students to keep editing with extra points for going beyond the minimum thresholds, for example? Or a competition for number of bytes, articles created, citations added (they could all have different weights and be evaluated in conjunction with quality checks).
I'd love to hear more thoughts on the topic since it's something I struggle with as well!
Tighe