This is a ton of emotionally charged verbiage about community interactions here, but at any point does this person say what they were using Elm to do? That seems like a pretty important point. Is this somebody who was just using the language recreationally, for their own amusement? And if so, did they have some expectation for the language community to be a source of (online) social interactions and connections with people?

Because if so, that really changes the significance of the accusations, in the sense that it makes them almost meaningless. "I wanted Elm to be my new life and my new friends and I wanted to shape it myself as a personal milestone but that stuff didn't happen and now I'm mad and I'm leaving" is a heck of a lot less meaningful to me than, "this language doesn't work well for the problems I'm trying to solve, and the maintainers aren't interested in adapting it to my problem domain, so I'm going to move on to some other language for this thing I'm working on".

I really don't care if someone is pissed that a language development community didn't make someone feel like they belonged to a social club or otherwise interacted with him in a way that satisfied some void inside of him. But if there was some actual purpose to his language noodling, as opposed to being purely recreational, it would be infinitely more interesting to know about how it fell short of the purpose, why the language fell short, why the maintainers didn't want to evolve it in that direction, and what language the author is moving to for their project that does a better job, and why they chose that language. That's meaningful. Anything related to whether or not they felt listened to or if they felt like they were on the inside or the outside is just utterly meaningless, it's like when people complain about news articles that don't have anonymous comment sections.

I realize that to a lot of people, the recreational community aspects of open source development are literally the only thing they care about. But I also realize that to some of those people, they don't understand that this is not the primary purpose of hardly any of the projects they care about, language projects probably least of all. Open source maintainers are not obligated to anybody to create a fun community for recreational users, with a well-lined pathway to becoming a recreational core developer. But that is clearly all that this person cared about, hence all of the emotional stuff which I just don't get. I'm not saying it's invalid, I just don't personally relate to that perspective at all.