How to add "load more" link to comments?
Views Infinite Scroll and many similar modules allows you just that.


  Views Infinite Scroll provides a Pluggable pager that enables views infinite scrolling ( autopaging, depaging, endless pages ...you name it) by using jquery.autopager plugin. using this module with views page display will load another page whenever the user reaches bottom of the page.


Views Load More is other example.


  Yes, this is indeed, Yet another load more pager for views.


And you can show anything with Views. Comments too.