Highly negative scores are not handled well
When a student views an exercise which was graded with a very negative score, a number of red "X" shaped symbols corresponding to the score is shown. So if the score is -3, three of these symbols are shown. If the score is -100000, that's how many of these symbols are shown. This makes the page pretty much unusable. Of course it is not likely that such a score will ever be given, but still it could be handled more gracefully. In my opinion it suffices to show one such red symbol and reveal how negative the score really is with a mouseover message or some other indicator. This would also solve the problem of not being able to indicate a non-integer score exactly.