I have a form where part the workflow is such:
1. Initiator completes form (result: SP "Modified by" field shows name of Initiator)
2. Reviewer rejects form by checking a radio button and entering comments (result: SP "Modified by" field shows: name of Reviewer, and then seconds later, reverts to name of initiator. Why does this happen?
3. If Reviewer edits the form again, the "Modified by" field changes to name of Reviewer and stays that way.
What doesn't the name stick on the first time the Reviewer makes the change?
I'd expect that the workflow is modifying some item properties. As the workflow runs in context of the initiator all updates to the item will be done as initiator so the modified by column will represent that user.
If you need to conserve the reviewer I'd go with a separate column "reviewed by" that holds the name of the reviewer.