Oracle specifically prohibits such disclosures in their *license* - it has nothing to do with trademark. Since Oracle is proprietary software you can't use it without agreeing to their license - when you download it for free you're asked to agree to a license online, too.
If you'll read the GPL closely you'll find no such prohibition on disclosure of benchmark or details of any other experience you have with .LRN.
Nor does US trademark law prohibit you from saying ".LRN(tm)" whenever you want as long as you acknowledge the trademark. The only purpose of trademark law is to protect the name and graphic from being stolen by others.
Also trademarks can slip into common usage if you don't defend it, as "xerox" has here in the United States as a synonym for "photocopy". If ".LRN" becomes the popular english slan noun for "web-based e-learning system" I doubt any of us will complain, though! :)
