I wish to conclude this series with a summary and TL/DR version of my previous posts, followed by some caveats.
Previously, I attempted to show that historical reenacting is valuable as a form of crowd-sourcing where historic sites let the public interact with a large number of amateur enthusiasts. Though many people that come to reenactments as members of the public are history buffs, the sheer amount of nerdy information hording manifested by reenactors is enough to provide a valuable service by introducing people to new bits of information and correcting the misconceptions of hollywood and popular history. Moreover, reenactors are a valuable source of information about the material culture of the time period that they portray, which can relate to all sorts of aspects of society or economics. This is both a valuable teaching tool for the public and a potential resource for scholars. In addition, reenacting is a major motivating force for modern amateur historians, the best of which can make some pretty interesting discoveries.
So there's more to the funny clothes and nerdy obsession with detail than meets the eye.
Caveats below the fold.
I'll conclude this final post with some caveats. My previous post presented a best case scenario of what reenactment can and does do. It did not address most of the innumerable problems that the hobby has. Most of these involve the ignorance (sometimes willful) of reenactors, which can seriously limit their use as educators, to say the least. This can range from 'Scottish' 'medieval' groups who are reenacting the (grossly inaccurate) movie 'Braveheart' rather than 14th century Scotland to Civil War Confederate reenactors who are willfully ignorant (or in denial) of the true causes of the civil war to WWII German reenactors that parrot the tired old cliche of the non-nazi, totally-not-evil-or-murderous Wehrmacht going about it's duty*. Groups that are simply inaccurate or ill-informed ('farby' in the more radical sense) can be kept out by quality control. But the built-in biases of WWII German reenacting and Civil War Confederate reenacting are much more intrinsic to a lot of groups, by my experience, and thus are pretty hard to keep out of any reenactment event (it would look odd to ideologically screen groups for 'good german' and 'lost cause' cliches).
You will also note that I did not touch on battlefield reenactment at all, focusing instead on the 'living history' of camp life presentations and public interaction. This is partially because my 15th century group doesn't do battlefield reenactment, so I've never done it myself, and partially because I find it harder to defend as an educational tool, unless it's viewed as a way to get people to come to battle sites and listen to a national park presentation.
The above are why this is a 'partial' defense of reenacting as an educational tool. It still is very problematic in a number of ways, though I do not believe that this is even across time periods -- Revolutionary War reenactors will often express the nuances and true causes of the conflict much better than civil war guys will, by my experience. This is probably because there is no need for either Loyalist or Patriot forces to apologize for their portrayal, and the American Revolution is not broadly a source of ideological controversy, in that there is not a large population of Americans who wished the British had won. Of course, this could just by my bias as a medieval reenactor who (like most of my reenacting buddies) wouldn't touch Civil War Confederate or WWII German portrayals with a 10 foot poll.
*Note that I do not say that they are Neo-Nazis. In general, though, WWII reenactors portraying Germans minimize or don't mention the atrocities committed by the forces that they portray, when in fact that Wehrmacht was an integral part in coerced labor, murderous 'anti partisan' campaigns that consisted of horrific reprisal killings (500 Russians or 100 Dutchmen for every German killed, sometimes, to say nothing of the Warsaw Uprising) and of course the Final Solution itself, where they sometimes played a prominent supporting role, at the very least. This says nothing of those that portray the Waffen SS, generally out of military-history nerd fanboyishness of a more questionable sort.