I just learned of the new role feature for attr_accessible because of this controversy. This seems to solve one of the major issues with attr_accessible - that different controllers and users need to update different attributes, so any somewhat complex app would end up widening it's attr_accessible attributes beyond what they should be.
These are still blunt tools though - what if only superadmin users can update a role column to superadmin, but admins can update it to admin or guest. This requires more extensive logic in the controller than simple attribute filtering, demonstrating why this filtering really belongs outside the model. Despite that, I think the new "role" based attr_accessible probably covers most cases and seems quite useful.
For all we know, GitHub may have been using attr_accessible but have expanded it to include columns updatable by admins.
Thank you for the thoughtful comment - perhaps there is hope that HN hasn't been entirely taken over by people talking out of their asses.