In all my trips to WDW in the past 7 years (which are 15+) I have encountered someone trying to rejoin less than a handful of times. I don't get how this is such a major issue that there are constantly threads like this on it. Only one of those times was the person trying to move up in the line rude and pushy. I know some of the tour groups can be problematic but I see that as a different issue.
I can only think of one time that I had to do it. My family and I became split up at Splash Mountain due to miscommunication. I went for fastpasses. My husband hadn't heard me say that I was getting them so he went in the line. Once I realized what happened, I had to pass approximately 20 people to rejoin my party. No one's wait time was extended and no one lost a seat due to me rejoining my family. In fact once he realized what happened he stopped and let other parties pass them up so there were a number of people who actually got to ride sooner than later. I'm sorry if you were one of those people who thought that I was some how trying to get over on you by getting a spot further up in the line but I'm not the least bit sorry that I rejoined my family. I said please and thank you to each and every group that I passed and I am thankful that they were all so courteous as to let me join my family. Normally, I would have texted him and said go ahead but it was a long wait time and it would have been over an hour before we would have been able to meet up again. That is too long to go without enjoying vacation time with my family. If you see it differently - that's fine. We will just have to agree to disagree

Common courtesy works both ways. I think it all depends on the individual circumstance. I would hate to think that everyone in this world is so rigid that they can't demonstrate some kindness every now and then.