Blackbird Spyplane is a newsletter written for enthusiasts: rabbit-hole shoppers who stockpile extremely specific saved searches on eBay as if it’s a competitive sport. There is nothing chill or low-key about it, other than a core appreciation for the kind of crunchy outdoor apparel once associated with chill and low-key people.

This is largely on account of the newsletter’s intense voice, which may read like a parody of a neurotically online men’s style writer — things he likes are “dope,” “fire,” “tasty,” “vibey” and “mad cool,” sometimes in all-caps — but is closer to a hyperbolic version of the inner monologue of Jonah Weiner, a journalist who started Blackbird Spyplane in May 2020 with Erin Wylie, a talent scout in industrial design for Apple. (Mr. Weiner is a contributing writer for The New York Times Magazine.)

Beneath that overstimulated voice, though, is sincerity. A newsletter that began as an outlet for “unbeatable recon” — fashion, culture and décor recommendations — and interviews with creative types about personal style has increasingly become a space for Mr. Weiner, who typically writes the newsletter, and Ms. Wylie, who edits it, to indulge their obsessions.

Mr. Weiner and Ms. Wylie, who live in North Oakland, Calif., have positioned themselves as unshackled from advertiser influences, much like zine writers. Also like zine writers, their audience is rather small by digital media standards, though not insignificant. Blackbird Spyplane is hosted on Substack, which doesn’t release specific subscriber numbers, other than to say that the newsletter has “tens of thousands” of subscribers to the free version, while “thousands” pay at least $5 monthly for additional content.

In the first year, the pair hunted for novelty merch and vintage ceramics and asked famous people about their niche shopping interests. They still do that, but they also publish longer essays on male hair loss and the curious color trends of cars; advice on how to make friends and “cop” responsibly (or not at all); decrees against things they deem “a bummer,” like heather gray tees; and treatises about why the aesthetic of 1990s coffee shops (shabby) is superior to that of modern coffee shops (Scandinavian). Everything is still illustrated with deliberately chaotic Netstalgic graphics.

“When it comes to style and fashion coverage, so much of it these days feels like marketing,” Mr. Weiner said. “There’s a lot of people who like the internet best when it feels handcrafted and misshapen and idiosyncratic.”

Substack doesn’t provide demographic information even to its newsletter creators, but, anecdotally, Blackbird Spyplane has a large media following, which makes it seem influential. Kaitlin Phillips, a publicist, said via email that “getting my client in Blackbird is the best way to mass email every fashion writer in New York, men’s wear and women’s wear.”

Yet while the newsletter has attracted female readers and Q. and A. subjects — like Sandy Liang, who spoke to Blackbird Spyplane about buying Polly Pocket toys on eBay, coveting a pair of Skechers she was denied as a child and other “things that shaped me as a designer, but I feel like aren’t highbrow enough for other people to care,” she said — its content has long come across as “dude-leaning,” as Ms. Wylie said, or “male-coded,” as Vox once put it. Absorbing the voice can feel, at times, like watching Dr. Jekyll (if he were a socialist) overcome Mr. Hyde (if he were a hypebeast), with one dressed in vintage L.L. Bean and the other in Homme Plissé Issey Miyake.

Ellen Van Dusen of the housewares and clothing line Dusen Dusen joked that the style had a “learning curve.”

“The first time I read it, I was like: ‘This is insane. I don’t even know if I can decipher what they’re trying to say here,’” she said. “The second time I read it, I was like: ‘OK, this is performance art. It’s funny. It’s a joke.’ And the third time I read it, I was like, ‘Oh my God, there’s so much valuable information in here.’” (Ms. Van Dusen once collaborated on a line of jackets with Ms. Wylie.)

And last week Blackbird Spyplane became a little less dude-leaning, with the introduction of a new vertical by Ms. Wylie, focused more on women’s fashion. It’s called Concorde, in keeping with the supersonic jet theme, and is written in her voice: casual, loose, because anything else “would feel really put on,” Ms. Wylie said a few days before the first edition was sent to all subscribers. (In the future, Concorde will come out twice a month for paid subscribers.)

“It’s her version of a much less deranged lunatic prose style than the one that I do,” said Mr. Weiner, who reversed roles with Ms. Wylie as her editor for Concorde. “If anything, I was like, ‘You don’t need to do the all-caps superlative here.’”

That’s because the Blackbird Spyplane voice, however distinct, isn’t everything to them. They believe their readers respond more to the energy behind it, “the notion of: This thing is going to show up in my inbox, and it’s going to just be fun,” Mr. Weiner said. “This isn’t a corporatized, algorithmic, A.I. version of a fun, friendly voice.”

“You could design an A.I. to serve up the disparate things that we connect,” added Ms. Wylie, who used her first Concorde dispatch to dissect her interest in the color silver, connecting a plate of Roman anchovies to a Bjork video to the 1990s designs of Martin Margiela. “But I don’t think anybody would.”

Ms. Wylie emphasized the “spinoff” would still have unisex tastes “because anybody can wear anything,” she said, and because that’s how she defines her personal style. She and Mr. Weiner, both 41, are a longtime couple (though they wouldn’t specify how many years they had been together) and they trade clothing. Recently he took ownership of a pair of her of Lauren Manoogian pants.

But from the earliest days of Blackbird Spyplane, Ms. Wylie has wanted to dig more into women’s fashion. She spent about a decade editing and writing for magazines, and before that worked at a fashion forecasting company. Two things have held her back: demands on her time from her day job and the fact that she and Mr. Weiner “err on the side of being anti-growth,” as he put it.

“We just have a general foot-on-the-brakes approach to this thing in terms of expanding it,” Mr. Weiner said. “We have no problem staying niche.”

That extends to the way they make money. They’ve turned down offers from major luxury brands, like a French fashion house that wanted them to embed its latest collection video in the newsletter and an online retailer that wanted to collaborate on a capsule devoted to small makers.

“Erosion of true editorial” is the reason Ms. Wylie said she left magazines in the first place.

“Everything I was being asked to do was sponsored or ad-directed, and that just didn’t feel good,” she said.

They also don’t accept gifts, an exceedingly rare policy in an ecosystem in which brands shower fashion writers, editors and influencers with expensive bags and all-expenses-paid trips in exchange for content. They claim to earn newsletter-related income only on subscriber fees, infrequent merch drops —  once they made shoes with a Finnish shoe brand called Tarvas — and minor earnings from purchases made via affiliate links to eBay or Bookshop.

“There’s something that is obviously dusty and throwback to this mentality, but we’re fine being dusty and throwback in this way,” Mr. Weiner said. (If it sounds like a scrappy operation, consider that Blackbird Spyplane has pulled in major names as interview subjects, including Seth Rogen, Lorde, Jerry Seinfeld and Andre 3000, some of whom Mr. Weiner has separately profiled. Its earnings most likely add up to six figures annually.)

“You open any fashion magazine right now, and I guarantee you there’s a bunch of clothes in there that no one on staff at the magazine thinks are especially cool,” Mr. Weiner said. “They’ve got advertisers to keep happy. If something’s in this newsletter, it’s because we think you’re going to like it. It’s a very straightforward proposition.”

As straightforward as possible for a newsletter that, within its most recent edition, used the following phrases: “cerebellum-bussin quasi-paradox,” “slapping ‘plant-based’ fits,” “jawn-polytheistic spin” and “roasted & toasted footwear.”