I’ve just suggested an edit to [a question which used xyz.com as a placeholder domain name](https://serverfault.com/q/601763). Lots of people are unfamiliar with [RFC 2606](http://tools.ietf.org/html/rfc2606), and therefore use domain names other than `example{.com|.org|.net}` as placeholders. Such domain names are [blocked from use on Stack Overflow](https://meta.stackexchange.com/q/208963) according to a [tag:STATUS-COMPLETED] [policy discussion](https://meta.stackexchange.com/q/186529), so why can they still be used here on Server Fault?