The problem is, unless you give everyone the ability to moderate all the time, not everyone will HAVE mod points - and as a result, only some students will get the ability to moderate, which is highly unfair if grades depend on these marks.
Conversely, giving everyone the ability to moderate cheapens the value of a mod point, and in some cases, still won't solve the problem - once a comment is as highly rated as possible, it can't be moderated up further - only down.
Additionally, if someone is moderated down enough, the lose the ability to post - denying that student the chance at further participation, which again would be bad, particularly if grades are a factor.
So, while I think this is an interesting idea, I'm unsure how it would work in implementation. You could change the default comment values, but that doesn't actually solve the problem, it only reduces it's frequency. You might also be able to prevent the default ban from being moded down, but I'm unsure how, other than making all the students admins, and that could be done if you kept their security level low enough.
Lastly, if you give them admin access (even at a low level) they will be able to see who moderated what, and how, potentially leading to retaliatory modstorms...
If you do go with slash, please let us know how you solved or addressed these potential problems.