Doing this is like saying "Hey you idiots, look how smart I am" to everyone waiting for their way in the right lane.
The lane is open until it is not, and as long as both lanes are open they are both "right" (in the non-directional sense, obviously). Why rely on clearly nebulous (sometimes variable, sometimes non-existent) social norms rather than concrete traffic norms? Use the open lane, or don't complain when others do. It's not asshole behavior, it's common sense driving.
There is no reason to take offense while driving so long as people 1) follow the rules of the road and 2) do not endanger others with reckless driving. Using open lanes does neither, and it only inconveniences the people that refuse to use the roads as they are intended to be used.
It's rude, and it demonstrably increases traffic.
It's an arbitrary game, and everyone makes up their own "rules of decency" and gets mad when someone follows the rules of the road rather than the rules of their head. Yes, people "know" about choke points, but that doesn't mean it's wrong (or rude) to use open lanes. So long as those lanes are open, they are going to be used, so everyone may as well make use of the space.
Is it my fault that others choose not to use those lanes? No. Is it your fault that it upsets you? Yes. It's not rude. I'm not being impolite. I wish everyone would just follow the same set of rules so we could stop being mad at each other. Which set of rules should we follow? I vote against the ones that change in with the person you're asking.
Having said that, I don't really like when people change lanes just to jump ahead of one or two cars. It doesn't upset me and I think it's fair game so long as it's done safely, but I empathize with the distaste for that a little more.
This is not only rude, but also blocks the other(s) lane(s) bringing traffic to where it wasn't before.
Its almost like say it's ok to pass in front of other people in the theater line.
This is true of unstopped vehicles as well. Not everyone is comfortable driving at the maximum safe speed. In fact, where I live, fines are enforced on all state roads from 6 to 13 MPH below engineering guidelines. Even so, many people choose to travel even slower than allowed by graceless statute. While these patient souls approach the bottleneck, several of the swift may de-queue themselves to the benefit of everyone who would otherwise wait behind them.
Oftentimes, the road hasn't actually reached saturation--it's just a compound case of live-lock and if people use the full measure of available lanes (instead of stopping at the first sign that says "Road Work Five Miles Ahead"), they have a greater opportunity of resolving the contention without promoting a cascaded slow down.
Of course, all of this is an edge-case. As the OP alludes, when the road is actually saturated, the real solution involves either decreasing demand for or increasing the supply of throughput at the chokepoint. Mere bickering and maneuvering will not avail anyone.
Please keep that line as short as possible by using all the lanes available.
Please leave exit lanes open by merging as soon as possible.
What really piss me off are drivers who move from the "right lane" into the "open lane", and then merge back after cutting perhaps 5, 6 cars.