I am on the way to develop a plugin to grant extra points for question edits.
The recent (q2a 1.8.0) point system can be overridden, but it is not that easy to customize. Here are gidgreen's replies from the past:
add a custom column to qa_userpoints via your module's init_queries(...) function and then override qa_db_points_calculations(...) in qa-db-points.php to add in the extra calculation based on that custom column.
It was done already with one plugin: https://github.com/arjunsuresh/q2a-betterpoints
Is that foolproof and future safe? Probably adding a prefix to the colum, e.g. q_editpoints?