One thing worse than what you described last week is when there is a road obstruction and people seem to think they have the right to cross the centre line into on coming traffic. Maybe you could address the legal side of that. My understanding is that on coming traffic has the right of way.
This reader describes something that is almost seems to be expected behaviour. The driver of one vehicle comes upon a perceived hazard such as a pedestrian, cyclist or parked vehicle and moves partly into the oncoming lane to make room. Oncoming traffic moves to the right to avoid the encroaching vehicle and most of the time there is not a problem. However, if there is no room to move right or the driver is not anticipating the move a collision may result.
The rules have been made for a reason, uniformity, predictability and the avoidance of collisions. The reader is correct, the oncoming vehicle does have the right of way and the encroaching driver is breaking the rules for the sake of convenience. Rather than slow or stop to let oncoming traffic by first, they will take a chance and put everyone at risk.
The Motor Vehicle Act does provide for crossing the line in some circumstances to avoid an obstacle on the highway. The driver doing so must have a clear view for a safe distance and make the move without affecting the travel of any other vehicle. The exemption does not apply when you must cross a solid line.