> Concerned Reddit users were quick to question what the site knows about them<p>Newsflash: Reddit knows everything that you have posted to it, including what can be inferred from that information. There's also no guarantee that the things you delete are forgotten. "Private" messages are not, in fact, private.
If you leak any particular detail of personal life onto both Reddit and another web site or possibly email provider, they can be correlated to identify you. One the correlation between identities is made, you're outed.