I heard Discord may have negative posts as well but I find the official D newsgroups (with a forum interface) very friendly and clean. Minimal moderation seems to help there.

The Discord is quite nice, you should join =)

I'm one of the moderators on D's Discord server.

We do our best to ensure everyone feels welcome to join in. Of course none of us have social media training and are just doing our best.

If something is going down and we are not taking action it may be because we are not aware of it being problematic and are always open to hearing complaints as they come up!

We moderate with a light touch to allow our users as much freedom as we can. People can write negative and bikeshed posts, and they can criticize me as much as they like. But we do moderate posts that make personal criticisms of other members, go off topic too far, or engage in unprofessional behavior.

To be honest, this just described your grand post.

Actually bikeshedding is discussion about software architecture. And software architecture is an absolutely valid discussion theme outside of stackoverflow.