From Wikibabel

We value your privacy, blah blah blah...

The only private information we keep is your email address if you provide it when creating an account. The only reason we ask for it is so that we can resend your password, if you ever forget it.

The wiki also keeps track of your login when you edit something, or your IP address if you're not logged in. There isn't much interesting to do with those, to be honest.