Support comparing entity versions
A long ago I supposed that users will describe made changes by means of comments that are obligatory fields for all entity changes. But this doesn't happen because of everybody is too lazy.
Thus, I suggest to get rid of useless and annoying comments but replace them with a much more useful feature, namely, an ability to compare entity versions. As far as I understand now we have a history for jobs and marks, so entity is either of them. Comparison for marks should show differences in fields, while comparison for jobs additionally should show differences for files like it is already done when comparing verification results of different jobs. Also I suggest to support comparing of various versions rather than just show changes made in a given version relatively to the previous one. For instance, you can see an example of an appropriate interface for that here.