It seems that every few years, a new anonymous-messaging platform enters the market; rapidly gains a fan base, investments and media attention; then crashes and burns. Usually, the cause is some combination of unfettered bullying, harassment or misinformation that blooms within the platform.

And yet, the apps keep coming. One of the latest arrivals is NGL, which invites users to solicit anonymous questions and comments from their followers on Instagram, Twitter, Facebook or elsewhere. NGL, the app’s website explains, “stands for not gonna lie.”

During June and the first half of July, NGL was downloaded about 3.2 million times in the United States, according to Sensor Tower, an app analytics firm. It was the 10th most downloaded app in the Apple and Google Play stores in June, Sensor Tower said.

“Anonymity has always been the secret sauce,” said Sherry Turkle, an M.I.T. professor who studies people’s relationships with technology. She said that the craving for anonymous self-expression was nothing new, pointing to the confessional booth in some churches as an example.

But, she added, the desire for anonymity has never been about anonymity itself. After all, in many cases, the promise of anonymity is false, or at best qualified — the priest often knows who the confessor is, and apps that collect and distribute secrets are simultaneously collecting their users’ private data. In fact, NGL, which was started in November, goes even further, offering users hints about their respondents for $9.99 per week.

“Anonymity is a way to open the door to a feeling of space and permission, to a liminal space between realms where you can express something true or speak something true that you can’t in the rest of your life,” said Professor Turkle, the author of “The Empathy Diaries: A Memoir.”

Harold David, 34, an administrator for a fitness company in New York, recently tried out NGL. “It’s fun to see what people will say when it’s anonymous,” he said. “Who wouldn’t want to know someone’s secret thoughts on them?”

He said he had seen a few friends use the app and expected “more crass or more lewd” comments. But, he said, “it was actually a warm flood of responses about people’s experiences with me, so it was a really nice surprise.”

The experience of Haras Shirley, 26, a school resource officer in Indianpolis, was not as positive. Mr. Shirley received about a dozen responses after posting a link to NGL on Facebook and Instagram.

“I figured there would be more questions about my transition, and I’d be able to give some insight into how to ask those questions appropriately,” he said. Instead, he said, most of the questions were shallow, asking what his favorite color is or what was the last thing he ate.

He understands the appeal of the app. “These apps give you the idea that people are interested in who you are and want to know more about you,” he said. But it is not for him. “This really is geared toward kids in middle and high school,” he said.

As quickly as the app has risen, it has run into criticism.

Anonymous-messaging platforms like ASKfm, Yik Yak, Yolo and LMK have long struggled to contain bullying, harassment and threats of violence. Messages on Yik Yak led several schools to evacuate students in response to bomb and shooting threats. Yolo and LMK, anonymous-messaging apps, are being sued by the mother of a teenager who committed suicide (the apps were integrated into Snapchat, whose parent company, Snap, was initially a defendant in the lawsuit, but no longer is).

Secret, yet another anonymous-messaging app, shut down in 2015 despite investments from major Silicon Valley players. In a Medium post announcing the company’s closure, David Byttow, one of it founders, wrote that anonymity is “the ultimate double-edged sword.”

Mitch Prinstein, the chief science officer at the American Psychological Association, said that on the internet, people assume that the opinions of a few represent a large subsection of the population.

“Anonymity,” he said, “makes this worse.” The result is that if someone leaves an anonymous comment saying your haircut is ugly, for example, you begin to think that everyone thinks your haircut is ugly.

NGL’s website says that its community guidelines are “coming soon” and that the app uses “world-class A.I. content moderation.” It directs users to the website of Hive Moderation, a company that uses a software to filter text, images and audio based on categories like bullying and violence. NGL did not respond to emailed requests for comment.

Pamela Rutledge, the director of the Media Psychology Research Center, pointed out that “you don’t have to use trigger words to be unkind.”

“If someone starts using racial slurs or whatever they can get past the A.I., you can block them,” Dr. Rutledge said. “But it’s hard to draw boundaries around the comments that undermine how you think about yourself.”

When Reggie Baril, 28, a musician in Los Angeles, posted an NGL link for his 12,000 followers on Instagram, he expected questions about his career. “I was very wrong,” he said. Of the 130 responses he got, there was “more hate than not.”

He read a couple of comments aloud during a phone interview. “You could be so successful but your attitude is awful, you won’t make it,” he said. “I’m not sure 2015 Reggie would like 2022 Reggie.” Another one called him “a social climber.”

He was surprised by the acidity. “I’m not a confrontational person in the slightest,” he said. “I love making jokes, being goofy and silly.” He decided not to take the comments personally. “I read a lot of insecurity in the subtext,” he said.

In reviews online, NGL users have said that the app serves them fake questions and comments, a phenomenon that technology-focused publications including TechCrunch say they have replicated with their own tests. It is not clear whether these responses are generated by the app or by bots.

Johnny G. Lloyd, 32, a playwright who lives in New York, downloaded NGL as a way to increase engagement on his Instagram ahead of the premiere of his new play. In the three times he used it, he noticed some odd submissions.

“I got one question that was like, ‘What girl did you text most recently?’” he said. “This doesn’t matter in my life at all. That’s barking up the wrong tree.” Another message was more cryptic. “It said ‘u know what u did,’” Mr. Lloyd said. “It was clearly for a younger audience.”

When Clayton Wong, 29, an editorial assistant in Los Angeles, tried out NGL, he received an unexpected “confession” that told him to search for a specific love song online. Mr. Wong was immediately suspicious. “I didn’t think the song was very good,” he said. “If this person knew me, they would know this isn’t something I would be into.”

After he scrolled through the comments on the song on YouTube, he realized dozens of people had received an anonymous “confession” of feelings that had directed them to the same video.

A musician friend of Mr. Baril’s, Johan Lenox, expected a “chaotic” NGL experience, but got the opposite. He was surprised people wanted to shield their identity when asking questions like what he does after performing or what it’s like to be a musician. It left him wondering about the point of the app.

“If you want to talk to somebody, how are you going to accomplish this by sending anonymous notes?” he said. He thinks NGL will meet the fate of other apps that disappeared as quickly as they appeared. “No one will talk about it again in a month,” he said.

Alain Delaquérière contributed research.