What are the best web forum software packages?

Discourse helps make forum posts conversational. It is highly configurable, but at the same time comes with sane defaults. It's built on ROR, so if you are familiar with this framework, it's pretty easy to dig in and understand how everything works when the documentation may be lacking in some areas.

HORRIBLE customer service. And they just announced that they are closing channels of communication for customer support. The setup is very complicated for anyone who is not a developer and they do NOTHING to make this easier. Rude responses to valid questions from support.

This is the best i've tried. I have also considered discourse, nodebb, vanilla, and PhpBB

Customizing and theming is really difficult.

very good