Yes, but then there is a prescribed compensation that everyone involuntarily denied boarding (IDB) is entitled. The vouchers is an attempt to avoid this IDB by getting someone to voluntarily fly later.

Plus, I am not a lawyer, but I think IDB means just that -- boarding. Once you board the airline cannot change its mind, not for commercial reasons (although it might be able to weasel out of that by getting everyone off and re-boarding without some people). Again, take with a grain of salt; this is just what I heard.

Well, yes, but established practice is to deny people the opportunity to board the plane, not to violently remove them after they've already been seated.

Seems like it may be crucial. I am really eager to see how it resolves!

Just because it is legally allowed or an established practice does not make it right

Lots of things were legally allowed established practices until they were not; people realized they were unethical and immoral, hopefully people will begin to realize this practice is also unethical and work to abolish legal overselling

Yes, lots of things that are legal or established practice are not right.

But overbooking is almost certainly right. Look, fact is that some pax won't show up for their reservation. Without overbooking, planes would fly emptier, wasting money and damaging the environment.

The airlines have fairly good predictions in most cases, and people have different preferences, so that almost always in the small number of cases where there is not enough space you can get people to get bumped voluntarily. It's really a win-win.

It's a terrible practice and it should be punished more so it will stop.