Keeping old comments data is small and relatively cheap to store. I'm sure they've kept backups. Probably even yearly ones for the past 5 years. Storage for text really doesn't take up much room. There's over 4,500,000,000 words in the entirety of Wikipedia. You can download it all right now if you'd like. An offline copy of wiki is currently about 95GB. Probably half the size of your last CoD game update.