Delete a Message
I changed recently from Firefox to Pale Moon, so I thought it was due to a forgotten block I previously swept with the (now non-working with my browser) YARIP extension. Thanks to show me it was just a new "item" on the site, Gamer 
Whatever you used to remove this "header", you have maybe selected too much for it: there are several nested div elements in that area and a javascript, so a too large selection could have wracked something? Did you retry with just the text of this "anti-anti-ad" selected?
@antp: what about the idea that the <div id="SiteLifeSupportMissing"> could be set as "display:none" (or "visibility:hidden", but it will then leave a gap in the display) for registered users? If I'm not mistaken, a simple "if" about the relevant variables would just mean 1 more line. Ok, 2 lines with the closing bracket if you write this "easy-readable", 3 with a comment
Whatever you used to remove this "header", you have maybe selected too much for it: there are several nested div elements in that area and a javascript, so a too large selection could have wracked something? Did you retry with just the text of this "anti-anti-ad" selected?
@antp: what about the idea that the <div id="SiteLifeSupportMissing"> could be set as "display:none" (or "visibility:hidden", but it will then leave a gap in the display) for registered users? If I'm not mistaken, a simple "if" about the relevant variables would just mean 1 more line. Ok, 2 lines with the closing bracket if you write this "easy-readable", 3 with a comment