Symptoms
When the Out-Of-Box Workflow Comments SmartObject is executed as a workflow participant, and that particular participant has View Participate Process Rights, an error is presented similar to the following:
"28023 User] does not have permissions to View the process "
Diagnoses
Typically, if a user has View Participate rights to a particular process, the user should be able to view any data regarding for any process instances they were participants in for that process, including the comments created for the instance itself.
As such, this behavior has been identified as a bug.
Resolution
A bug has been logged for this behavior (Bug 507598). The current workaround is to give the users View rights instead of just View Participate in order to view the Workflow Comments for a process they are participants in.