Just dropping my $.02 worth. While I have not read every post in this topic, and not sure if anyone has pointed out an obvious yet. But I can see why a series would be locked even if it isn't completely correct.
One reason would be some user has taken it upon himself (which i did when i first got into this site for a series I thought was marked way wrong (Grand Designs)) and after being asked to cease and let the mods take care of it but still went ahead and changed it again, a MOD would lock it so that he does not have to spend what little spare time he has to fix other stuff, re-fixing what some user has changed without going through the proper sequence of events to get a change done.
Now while I understand from a users point of view we want our series to reflect truly the complete series and that our libraries metadata is correct when we choose to watch something, and it gets mighty frustrating when we know a series really well because we watch it constantly and like to think we know just about everything there is to know about our favorite series only to find that metadata scan for the library has trashed the sequence or renamed episodes in a completely different order.
My past experience is Moderator for one of the top gaming sites 3 years running (UT 1999 - 2001) DAMIT Clan servers, and I was known as a mean admin cause I didn't put up with BS from unruly players using our servers, but everyone wanted to use our servers because we didn't have a lot of unruly players. Also I have many years in customer support and can appreciate the frustration from both sides.
Final word, with all that being said, I find this site extremely useful, and for controversial series I just use whats posted and make sure the episodes are named and numbered correctly before renaming them.