Remove your Instagram account permanently or temporarily.
It's recently been claimed that Facebook is using smartphones to listen to conversations and collect data about users.
You can create a custom URL for your Facebook Group -- similar to how you can with Facebook Pages.
If you're the administrator of a Facebook Page for your business (or whatever), you can still comment as yourself.
Your facebook username allows people to quickly access your facebook profile: for example, http://facebook.com/benderisgreat.