===== Cleanup Comments =====

This script allows to delete comments with specific text in the content of the comment, in this particular case in ticket ABC-123 any comment containing "bla bla bla"

<code java>
import com.atlassian.jira.component.ComponentAccessor
import com.atlassian.jira.issue.IssueManager
import com.atlassian.jira.issue.MutableIssue
import com.atlassian.jira.issue.comments.Comment
import com.atlassian.jira.issue.comments.CommentManager

String issueKey = 'ABC-123'

IssueManager issueManager = ComponentAccessor.issueManager
CommentManager commentManager = ComponentAccessor.commentManager

MutableIssue issue = issueManager.getIssueObject(issueKey)
List<Comment> comments = commentManager.getComments(issue)
comments.each {comment ->;
    if (comment.body.contains('bla bla bla')) {
        commentManager.delete(comment)
    }
}
</code>

Reference: https://community.atlassian.com/t5/Jira-questions/Bulk-Delete-Comments/qaq-p/368877