They tell you to ride in the middle of your lane to increase your space cushion from other vehicles. It also helps to keep drivers in the same lane from going around you. If you ride to the right, they may try to squeeze past you on the left. If you ride in the left tire track, cars may try to squeeze past you on the right. I've had that happen at a red light where the car was turning right on red. Splitting lanes where I ride is neither legal or illegal. It's not part of the official vehicle code, (there is a governor-signed bill saying CHP may develop "guidelines", but they are not lawmakers) so drivers are used to bikes lane filtering and may be more comfortable moving alongside your motorcycle.
I vary which tire track I'm in depending on traffic conditions and if the center of the lane is clear of grease and oils, I'll also use that. Not much rain here. Opposing traffic will drift over the line and into your lane, especially texters, so the left tire track is more dangerous for hitting another vehicle head on and you'll lose big time. However, due to cars pulling out from the right and into traffic, you are also at risk. I lost a friend that was riding in the right lane, right tire track when a guy in a lowrider pulled out from a bar and stopped with his front in the right tire track. My friend T-boned the car and suffered brain damage. He lasted 6-months in the hospital.
You have raised common-sense guidelines for using the entire road. An alert rider will 'read the road' and its drivers, and adjust his/her path to minimize potential conflicts. Coming up to a busy shopping center? Better to be in a left lane than the right-hand one, because of exiting drivers from the shopping center. Don't forget the "
Oh, I am gonna miss the turn-off to the shopping center!" drivers who attempt to cross from the left lanes to enter the shopping center, cutting everyone off.
I don't agree with
RedMax's idea of "make a decision to stay up on the bike or lay it down." Few riders are skilled-enough to actually 'lay it down.' The only ones I can think of who might be capable of doing that are flat trackers, enduro and motocross riders, and maybe roadracers. I am sure that all those would agree a bike still on its wheels has a much better coefficient of friction and control over its intended path than a bike and rider sliding across the pavement. Doing a 'Superman' posture as you depart the bike may not cause much trauma, but the landing surely-will! Things happen so-quickly that most of the time, the unfortunate rider will only be able to think, "
WTF!?? &*^#@#!! as the impact happens.
My thought is that as the incident happens, perhaps the panic-braking bleeds-off enough speed that the rider, attempting to get past the car, dropped furniture, or other hazard will low-side as they ask the bike to avoid the impact via their behavior in the saddle. Something happening at higher speeds is likely to cause a high-side, as the rider brakes violently, and makes a choice to go either right or left and goes over the handlebars as their momentum parting company with the motorcycle puts them into that 'Superman' posture.
I think it was a Kevin Cameron article where he wrote about a road-racing get-off where he described sliding across the pavement, and adjusting his position to avoid abrading a hole through his racing leathers, as he felt the heat through the leathers. Today's gravel run-offs are much more forgiving than yesteryear's barricades. Plus, we have the CE armor affording better protection. And don't forget the helmet technology improves over time, helping to prevent a traumatic brain injury. Lastly, we have advances in medical care, and such things as Level I and II trauma facilities for the care of the unfortunates who need it. I once was running a group of paramedic students through hospital rotations, and we all happened to be meeting in the adult E.R. when two trauma alert patients came-in from fire-rescue. One was an off-duty police veteran, who had been riding a scooter in a t-shirt and shorts, and no helmet. If he had been AGATT, instead of his 't-shirt/shorts' "armor" I suspect his condition would have been much-different.
As riders, we make decisions about our riding apparel and our behavior while in the saddle. The prudent rider will maximize his/her chances for survival via the choices they make.