In the Workflow is used standard COMMENT Transiton screen. In the WorkFlow transtition is used validation: Comment Required Validator.
When trying to make a BULK change - Transition. The Field Comment can not be Edit (there is not Field Comment in JIRA)
The Comment Field is not shown. The Validators may the ignore the Bulk changes?
There is a way, how to solve it (Create Other CUstom Field and Fill it as a postfunction to COMMENT) but this is not systematic solution.