Can an extended journal version of a conference paper include different list of co-authors? If a conference accepted a paper with 3 authors, and the 2 co-authors were mainly reviewers. When submitting an extended version to a journal, should the co-authors be included or they can be removed? Can the paper include new authors?
If the work is extending the original, then all of the original authors should be retained.  New authors can certainly be added, however, if they have contributed to the extension.