I don’t have a link, but the lemmy creators (and maintainers of join-lemmy) answered this in a AMA about a month ago. They said they’d prefer the horrible people concentrate in their own instances so we can block them easily rather than have them in our instances. The join lemmy list does not serve as an endorsement, but a catalog of all available instances.

Neither burggit nor comfysnug are shown on the instances page.