To perform tasks in batches, select single or multiple comments in the 'Comments' view and click the 'More Options' button at the top right to see more available options.
Select 'Task - For Mark As A Read' to mark unread comments as read. A window appears, displaying a list of selected comments and an option to complete the tasks associated with them.
Click the 'Mark as Read' button to complete marking unread comments as read.
File Comments Batch Processing
This article helps you understand how to use batch processing options while in the Comments view.