During the work on changes to the grade book for Moodle 2.8, assumptions seem to have been made by developers that changing past grades would be acceptable if the new calculation was more "correct" than the old one. From our perspective, and from the perspective of many other institutions we have heard from, it doesn't matter what bugs have been found or what philosophical differences of opinion exist about how grades "should" be calculated. We can't have previous grades being altered without manual intervention and approval.
We are asking for assurances that from now on, maintaining integrity of grade history (and student data history in general) will be a top priority for Moodle HQ, in order to allow our institution to continue to plan to use Moodle as our LMS. If a grade calculation change is made, that calculation change must be manually approved per change, with the default to keep the value as it was, rather than defaulting to the new value. Grades with out-of-date calculations can be flagged for review by anyone who is authorized to edit that grade. Batch changes must be optional and should allow for selection by criteria such as course category, course start date, etc. to exclude completed courses or other courses whose integrity must be maintained.