Only marking the positives, for example noting only the good things that candidates had done through their work, is not appropriate as it does not form a balanced and critical view of the work. Marking should note both success and error, so that a final balanced judgment can be made.
There should not be any marking of drafts, as improvement is the responsibility of the candidate. A teacher may offer general summative advice (eg. You need to check your spelling accuracy), but they must not indicate or correct an errors on the draft. Neither should these errors be verbally communicated to the candidate.