If the author of a KB article is not also a Knowledge Manager, they can only edit the fields (ex: Knowledge base/ Configuration item) once selecting ‘Check Out’.
The behavior seen is due to the custom ACL kb_knowledge.* This ACL will only allow write access to fields on the kb_knowledge form when the article is not retired and the user has 'knowledge_manager' role. This is a custom created ACL which is not found in an out of box instance. When this ACL is deactivated, the user has access to all of the fields mentioned (when article is not published). When the article is published, they still will not have access to these fields (expected due to article versioning).