Elon Musk “doesn’t seem like” the right person to own Twitter, the social media platform’s co-founder has said, adding that improvements to morale and content policies at the business have been reversed under its new proprietor. In an interview with the Guardian, Biz Stone said positive changes he had helped oversee in recent years had been unwound by the Tesla chief executive. Stone said running social media companies is “not really a win-win situation … it’s always tough”, because “50% of the people are gonna be happy, 50% of people are gonna be upset with you”. “You have to be OK with stuff that you just don’t like or don’t agree with being on there,” said Stone, adding: “Otherwise, you should just go buy a magazine or a newspaper or something where it’s OK to have a specific leaning.” Asked if Musk was the right owner for Twitter, Stone said: “It doesn’t seem like it right now, but I could be wrong.” Musk has come under fire for temporarily banning journalists from the platform and reinstating previously banned accounts such as those belonging to the former US president Donald Trump and the self-proclaimed misogynist Andrew Tate. Stone, who co-founded Twitter in 2006 with Jack Dorsey, Noah Glass and Evan Williams, returned to the business in 2017 at the behest of thenchief executive Dorsey to “guide the company culture, that energy, that feeling”. Stone said improvements during his four-year stint, particularly in morale and overseeing content, have been lost under Musk. “We made a lot of improvements in those areas. And that’s all gone now.” Musk has rowed back on a pledge to establish a “content moderation council” that would have overseen big content decisions and account reinstatements, instead relying on more arbitrary methods such as user polls hosted on his own Twitter account. He also fired approximately half of Twitter’s workforce within days of buying the business for $44bn (£35bn) last year. Stone added that employees should not have been named as part of the release of the so-called Twitter files, a series of internal documents detailing decisions such as the suspension of Donald Trump. “When that happens, people get a lot of harassment,” said Stone. “It’s really bad.” Twitter’s former head of trust and safety, Yoel Roth, was reportedly forced to leave his home when Musk posted tweets misrepresenting Roth’s 2016 academic thesis, “Gay Data”. Stone said the concept of Twitter would survive, regardless of the company’s current financial struggles. “I don’t know that Twitter as a company is going to succeed for ever but the idea of Twitter I think will be around,” said Stone, pointing to the success of alternative platforms such as Mastodon. “It would only matter that Twitter the idea continued. And that’s happened. That seems to be happening already. Mastodon seems to be winning the open-source, decentralised version of Twitter. People seem to be going there.” He added: “I don’t know the future. I don’t know what’s gonna happen and maybe things will be great in a year and [it] had to go through this trial by fire. But, right now it does not look good, I would say.” Stone spoke to the Guardian as he confirmed he is joining the board of Chroma, a Swedish startup in which he is also an investor. Chroma creates an audio-visual experience for mobile phone users, describing itself as “a world of sound experiences in a pocket” where users can change what they see and hear. Describing Chroma’s work as “soundplay”, Stone added: “It’s a new way to interact with sound and to play with sound.” Last year Chroma collaborated with Venezuelan musician Arca to create Lux Aeterna, an app that creates an “ever-evolving, boundless audio-visual world”. Stone said his investment philosophy is simple – “do I like this person” and “do I think they can pull off this thing I would use myself?” He adds: “If those two answers are yes, I’m usually in.” Referring to Chroma’s CEO and founder, Andreas Pihlström, he said: “I like working with Andreas. He is a really talented designer.” Stone’s co-investors in Chroma include Evan Sharp, the co-founder of digital pinboard platform Pinterest, and Ben Silbermann, the co-founder and CEO of Pinterest, where Pihlström worked as a creative director. Stone, who has also invested in the messaging service Slack and Pinterest, added that he never thought of Twitter as being successful when he co-founded it in San Francisco. “I tell young people – if you’re doing something to try to get rich, it’s probably not going to work. You should do something that you’re just really enjoying working on and then you actually have a greater chance of becoming wealthy.”