When i was Playing my Tyranid Campaign, i wanted to get rid of one of my fleets to save money so i've sent it to die. It didn't die on first attempt but what it did was gain over 5000(!!!) renown for LOST battle. On next turn when i sent it again it gained similar amount.
I made new fleet and sent it against different system (weaker) and i still got over 2k renown. I also tested it on Imperial Navy Campaign and got similar results.
I don't think that was intended.