Also a previous answer I gave:
You could write an eloquent join query and paginate, example is not your data but call pet owner the main comment and list of his or her pets nested comments, same idea.


Here jimmie has 3 pages, when you click page 4 it goes to another pet owner.
Sorry just done quick no formatting.
I just did this query as a quick example:
$pets = Powner::query()->leftJoin('dc_pets', 'dc_powners.ownerid', '=', 'dc_pets.ownerid')
->select('dc_powners.ownerid', 'dc_powners.oname', 'dc_pets.petname')
->orderby('dc_powners.ownerid')
->paginate(5);
Page 1, page 2, page 3 is jimmie or say main comment
page 4, page 5 is diane
Under is list of pets, in your case sub (nested) comments.
Or
Just double paginate:

Have a "next main comment" button and a link for next set of nested comments.
This nesting can take a little work, usually no quick easy solution. @Snapey once posted a double paginate solution: http://novate.co.uk/using-multiple-pagination-links-on-one-page/
Or
Use ajax with divisions.