Under my answer in Space Exploration SE I just added the comment:
Note: I'll point folks back up to the comments under the question and to the other answer(s), both of which contain a wealth of additional informative information.
In my personal experience I come across plenty of information that I do not personally find particularly informative in a given context.
But when I write "informative information" to others, does it look like I'm being redundant, or is it something that is likely to make sense to most people? Is there a different word that would do the same job but not be so hard on the eyes?
Both additional and informative seem to be adjectives describing information, if I kept it, do I need to insert a comma?
It just looks wrong, but I can't put my finger on why.