Looking for a modern day wiki for a group project
My answer to Looking for a modern day wiki for a group project on Ask MetaFilter
GitHub offers a wiki for each repository. It’s free for public projects (no need to upload any code, just create a repo and ignore the other tabs) of you can pay $7 monthly for private ones.
With public wikis you can still control which users are allowed to make edits.
The only missing feature in your list is WYSIWYG editing, but they do offer a good “preview” tab.