Maybe arglebargle isn't understanding the purpose, maybe they are...I can't really say. I'm quite certain I do understand the purpose...but having a purpose and being the best way to achieve that purpose aren't synonymous. I think the "best way" would be the one which most reliably prevents the abuses you mention while best limiting collatoral damage from the policy. Returning to the OP, when talking about the author's motivation for writing a work, there can be no more authoritative source than the primary source. A secondary source would necessarily be *less accurate* than the primary source. A policy which fails to recognize those sorts of nuances is not doing a good job of limiting collatoral damage, regardless of how pure its purpose might be. To me, this whole issue with the "no original research" policy reminds me of the "Zero Tolerance" policies that you often see lambasted. The similarity being that in both cases, little to no leeway is given for discretion, there is no consideration of context or nuance. And so we see an author being unable to verify that their inspiration for writing something was X; and we see kindergarteners suspended for having GI-Joe sized miniature weapons in their knapsack. In neither case is the true purpose really being served. Instead, people are abdicating thought and debate to policy, attempting to absolve themselves of responsibility for dealing with a world that is not full of bright line distinctions.
To the latter point, that verifying people are who they say they are is difficult, I concur. Verifying that sources are reliable is difficult as well. Wikipedia editors seem to believe that the latter is at least worth a reasonable effort. If the case merits it, why would the former not also be worth a reasonable effort? For example, if you have a professor at a university who wishes to address some aspect of an article about them or their work (such as what inspired them)...would it really be that difficult to verify the source? Most, if not all universities seem to have public directories available, many professors have web pages on their departmental web sites. Wouldn't a quick email to the listed address for the professor suffice to ensure that the source has been reasonably verified? Certainly not conclusively...but Wikipedia can't possibly have "conclusive" as its standard. Even the standard you have for the article you refer to, "peer reviewed", doesn't "conclusively" establish anything, it just gives a good chance that the information is as accurate as our current understanding allows.