I have yet to find a community that has gotten popular and hasn't turned into a sewage plant. I think it's just a reflection on what the general population is like... :(
Emily Dunham of Mozilla has a talk about this Community Automation: https://www.youtube.com/watch?v=dIageYT0Vgg
Name a large programming community that is pleasant to interact with for newcomers and insiders alike.
It's a level of purposeful design that only the .NET and Go ecosystems approach, and because it's unusual and largely unobtrusive, it's not obvious that this really good, highly productive community is not at all accidental.
I would say that most large programming communities split into multiple communities, so different kinds of folks don't interact as much: the people on the core developer mailing lists are mostly not the same people as on IRC, or on user mailing lists, or working on issues for 3rd party frameworks in GitHub. I can't think of a sub-community that I've had experience with that I would characterize as unpleasant.
This resonates well with me. I came from PHP and I decided to learn C in order to contribute to an existing PHP extension. I was doing well following a C tutorial. Until I arrived at string manipulation at which point I said, f* this sh.
So looked for an alternative systems programming language to learn, and found Rust. And its a pleasant language to work on. Its a low level language that feels like a high level language.
My only fear is that, if Rust becomes a popular language, the community will end up as toxic as the JS and PHP community. Right now, the Rust community is filled with the smartest and friendliest devs I know of among open source communities, and I kinda like it to stay that way.