How would that be different from grading things under the current system?
Maybe exams should be layered - first, a test on basic terminology understanding, then a lottery of commenting on scientific research (1 ticket = 1 article).
Under the current system, grading is (relatively) easy because all you need to check is whether the answer given matches the correct one.
The proposed system would involve answers that cannot be mechanically pattern-matched and would need a LOT more time and effort to grade.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.