How to display comments of current node in a view
You need a contextual filter.  In your view, remove comment:nid from the Filter Criteria.  

Next, on the far right, under "Advanced", add a "Contextual Filters" and select comment: nid there.  



In the configuration options, under WHEN THE FILTER IS NOT AVAILABLE, select "Provide Default Value".  From the Type dropdown, select "Content ID from URL".  



Click Apply, save your view, and add the block as normal.