As I am writing this I don't see a way to reenable that checkbox (I'll keep searching). FWIW the Console help says the following about that checkbox:
If you deselect “Automatically send diagnostic and usage data to Apple”, you will no longer see the option. When you encounter one of the events described earlier, you’ll see the message asking if you want to send diagnostic information to Apple.
So unless I can find a way to reset it (haven't looked at plists yet or did any real research) it appears to be a one way switch. Once thrown, it's off, period.
Just found this which only repeats what Console Help says: