That said, he also had a strong tendency to reach some conclusion on a controversial topic and then defend it to the death, even when most of us felt that the ultimate answer seemed unknowable or even fairly firmly different than what he claimed. His arguments were based on immense textual knowledge, followed up with emphatic assertions of truth if you dared disagree, and intense flames if you gave him the slightest excuse to get personal. He said, at times, that the rest of the newsgroup had a grudge against him and that people arguing against him were rejecting Tolkien's words or not arguing in good faith. For quite a while I remained on cordial terms with him and with everyone else, but at some point he decided that doing that constituted me enabling what he viewed as their toxic behavior, and we haven't interacted as friends since. All that is to say: the guy knows his stuff, and unless you're a top-tier expert he'll argue circles around you, but I still don't trust his conclusions on controversial topics.
If anyone wants a more balanced look at the Elf-ears question (from the same era when Michael wrote this FAQ, I think, or at least compatible with it), I've got an essay by Conrad Dunkerson on my site: http://tolkien.slimy.com/essays/Ears.html
His analysis of the line, "it was LIKE a great shadow, in the middle of which was a dark form, of man-shape maybe yet greater" is deeply flawed. He argues that since a simile was used to describe the Balrog's darkness (and it has darkness), then the simile used to describe its wings means it has wings. Tolkien says "like a shadow" because it's dark like a shadow but it's not a shadow because shadows don't have physicality like the Balrog's darkness. We're clearly talking about a supernatural phenomenon that the english language can only describe via simile. Tolkien's abandonment of simile in later passages is to simplify the language. Repeating the exact same simile over and over drags the writing down.
Here's what we do know about balrogs, their essential characteristics are darkness, fire, speed, strength and magic. Flying is not an essential characteristic. It's never mentioned directly, and description of their rapid movement tends to be very metaphorical. We also know that if they do fly, they don't fly like dragons or eagles because they played no part in the conflict between the dragon and eagles. Balrogs were tossed aside with all of Morgoth's unflying creations. Only flying dragons specifically posed any threat to the Valar, and that was because of their flight.
(And all these years later, it's nice to see that Michael is being reasonably explicit about that issue in his own writing on the topic. It's interesting to compare this 2010 archive link to the current version on his site: after he says "Yes, the Balrog had wings", he's now added a clarification that "The wings were simply shapes made of darkness." Though in the link later in this thread, he evidently can't resist one final jab at anyone who disagrees with him: "I like the book the way it is without all the rewriting and propaganda". And he describes other people trying to discuss the topic as "long-winded nonsense essays". Honestly, I haven't missed those bits of interacting with him.)