buy a better monitor jj. Good point, we'll add an unstick on our todo list.
NO. This is just as bad. I loathe sites that require me to take action to make browsing sane just as much as the current situation. Each site that does this has its own way to make it unstick and I won't even bother looking 15 seconds how to hide that crap you're sticking through my optical nerve to read some content I may or may not even be interested in.
Solution: show your header for a second or two, then roll it up, leaving the bottom rounded part shown as a hint. If the user wants to show it again he will reach for that middle rounded part, upon which you could react to a hover, a click/tap and/or a drag. Why does it suck less? The animation builds expectation and explains the behavior, while the hint explains how to take action. Zero thought needed, and no friction to 100% content.