For DNN users looking for a business solution to this problem:
You can create another forum perhaps called 'Spam' but hide it so only administrators see it. If someone uploads an objectionable post, just move it to the hidden forum. That way they are not sent an email at all. You can probably then delete the entire forum from time to time to keep things tidy.
The other bug, where the notification checkboxes don't work, can also be sorted in a similar fashion - just don't display the text associated with the checkboxes and/or rename the checkboxes to something so users think it's doing something else. (I've got one notification checkbox renamed to 'HTTP Recognition' although it does no such thing and for the other checkboxes I have hidden the text.) This forces users to subscribe to the forums, which if you have a lot of forums like I do, is probably better anyway.
Another user has pointed out in this forum that users can use the bug free Active Forums instead of the Core DNN one. However, the DNN Core does have an advantage in that you can use it as many times as you like within a portal - the commercial one has a limit on how many instances you can have.
Jess