Lots of good points in your post. I'd only add that Nikon, like most other major manufacturers, maintains a Brand Guardian position or department of some sort which employees a small team of people who are tasked with monitoring how the Nikon brand is being used externally, and who also review various print publications and web sites/blogs and so on which comment on Nikon products. Many major retailers do the same thing. Whether or not such teams for various companies are large enough to actually cover all areas of concern is another matter. They rarely meddle in anything online or in print, but rather advise the corporate legal department about various issues extant.
I think the worst thing a company can do, unless there are extremely important factual inaccuracies in an op/ed or review or news article about its products, is to participate in a discussion thread in order to correct some perceptible inaccuracy. Any such participation is a very good way for the Nikon employee to get eaten alive in some forums. There are forum sharks out there who fully realize that a so-called brand guardian or product evangelist is limited in the degree to and manner in which which he or she can respond if a thread becomes heated. The forum sharks of course have no such strictures and will proceed to eviscerate the brand employee without mercy. The issues may end up ranging very far indeed from the original point, but that makes absolutely no difference to a bunch of trolls and sharks who smell blood in the water. For a brand employee in that situation it's tantamount to ritual suicide.
Several years ago, my research company was approached by a rather prominent brand about just such a prospect - brand guardian and product evangelist participation in online discussion boards/forums specifically to correct misinformation. The test that my business partner and I presented online for the edification of the brand owners was enough to scare them all into about a week of nightmares. On that basis they elected to follow our advice and stay well away from surreptitious guerilla marketing (i.e., fake forums posts), online product evangelism in discussion boards/forums, and anything other than absolutely transparent guerilla marketing. They're happy they did so. A competitor of the company shortly thereafter decided to battle the current and ended up embarrassing itself.