I see a lot of people emphasizing to new users that "mastodon is not twitter", in a way that I suspect alienates those users while also being misleading.

Mastodon and mastodon-like fediverse nodes (ex., pleroma, gnu social, etc) look and act almost exactly like twitter, very intentionally.

To the degree there are technical differences, they are largely either scale-related (the fediverse was federated since long before mastodon was a twinkle in gargron's eye, because centralized social media is only possible with stupid amounts of no-strings-attached VC money) or downstream from culture.

Almost every technical decision that differs from twitter here is downstream from culture, and almost every technical decision that isn't different from twitter is the result of the culture not yet having enough discourse to change it.

What is the culture?

The culture on the fediverse is formed from ex twitter users -- people who left twitter in various waves at various stages. These waves are mostly people who felt like they didn't fit in (or who felt actually unsafe) on twitter.

The first wave predates mastodon by years, and was open-source / free-software / security / privacy / civil liberties people. Basically, the kind of guy who tries to get everybody he knows to use tor & kali linux. These folks felt like the proprietary nature of centralized social media software was an ethical problem, and that the centralization & ad-based monetization was a security risk.

Later waves include: furries, LGBTQ people, and non-white people, all of whom faced systematic harassment on twitter; anarchists and communists, who don't like the profit motive in general and were happy to move as soon as they were aware that something else was available; retrocomputing / slow-computing people, who felt that centralized social media produced an unhealthy and environmentally unsound relationship between people in social media; sociology-of-UX & software-utopianism people, who felt that centralized & profit-driven social media produced unhealthy relationships between the people it mediates.

These categories overlap, and the more of these categories you fall into, the more likely you've actually been on the fediverse for a while. (For instance, I'm an anarchistic free-software guy with sympathies for slow-computing & software-utopianism, so all of the concerns other than systematic harassment have affected me personally, & I've got a lot of friends who have gotten systematic harassment too, so I've been on the fediverse for a good half-decade.)

Anyway, despite the fact that the fediverse is populated mostly by people with strongly-felt objections to the way things work on twitter, these cultural concerns actually only rarely result in visible technical changes -- and even then, they tend to be subtle. Emphasizing the technical differences is probably not helpful for onboarding new users, because new users are unlikely to encounter them on their own for weeks or months! To a new user, mastodon looks like twitter with a different color scheme.

It is more useful, in my opinion, to emphasize to new users that the fediverse, in general, cares about the users that twitter was happy to subject to harassment & other forms of violation long before a Musk regime was on the radar. Then, when a user encounters a technical difference, they are primed to understand it as downstream from culture: they know that it's somebody's attempt to fix a social problem that was rampant on twitter, and every former twitter user is aware of the kinds of social problems that were rampant there.