Whatever you ever filled in or posted to the servers of a private company under your real identity is "data about me that has been collected by private companie

Whatever you ever filled in or posted to the servers of a private company under your real identity is "data about me that has been collected by private companies". It's not that complicated. Most places now (for compliance reasons) allow you to delete old accounts and old posts either through a button or if you email customer support or the webmaster.