While "keep right except to pass" is technically the law here in Ontario, the de facto standard is that the middle lane is the cruising lane, the left is the passing lane, and the right is basically a second merging lane. This means that it is not uncommon to have stop-and-go traffic in the left two lanes while the right lane is still moving and mostly wide open. Drivers will frequently move right into the middle lane from the ramp even with no traffic in the right lane and not having sped up to the highway speed. It's an complete waste of resources.

Highways are a complicated graph problem I guess, which I'm not very good at, but I wouldn't be surprised if the true bottleneck was some offramp later. So, increasing the throughput of the road leading up to it shouldn't really improve things, right? And leaving rightmost lane less heavily populated might make it easier for cars to do the off/on ramp thing which might make things easier around the bottleneck.

I dunno. People pack in as tightly as possible around here and we still get traffic. I think it is just inevitable.

Going onto the IdiotsInCars subreddit, it's kind of shocking how commonplace it is for people to undertake other road users by speeding past in the slow lane. It's already more difficult to merge back into a slower lane because you have a much bigger blind-spot (and have to twist your neck a lot more to get a good look), so it doesn't make it any easier if you have to expect that people will be speeding to undertake you.