Sometimes technicians will go into an incident, decide they don't want to work on more difficult issues, and back out of the record. Other times, technicians or managers are reviewing an incident, but don't assign it to themselves as they are just watching status.
To capture these "task reviewers", you could report off the Transaction Log and the task table to create a report. The issue with this is that the tables are large and that can be difficult to create an efficient report.
The customization in this article will capture this situation in a table for reporting and monitoring.