Crossing any unbroken line in the center of the road here in UK, apart for a few specific reasons, such as passing a stationary vehicle or to take a side turn on the other side of the road, is liable to get you a $100 fine and three points on your licence. Getting points means more expensive insurance and twelve means a driving ban.
Some years ago a good friend of mine got caught clipping the first part of a single unbroken line with one front wheel (!) after an overtake of a slow driver and got prosecuted; but more than anything, the policeman was probably jealous of him being in his late teens but being able to afford a Triumph TR6 sports car (although he had truly earned it, working on an oil rig for almost two years).
I remember being on my Honda 750 and overtaking a car on a wide country road, after a bend, on a straight (not across an unbroken line). The driver of an oncoming car, a few hundred yards away had a similar crazy reaction to the one you encountered; headlights flashing, horn blaring, fist shaking, mouthing off. However, by then I had been well and truly back on my own side of the road for quite a distance and the oncoming car was so far away I had time to take one hand off the handlebars, stand up on the footrests and give her a friendly wave. There was no danger to anyone, nor did I break any rules. My reaction probably completely freaked her out.