https://www.youtube.com/watch?v=ZPfB6B6XrAU
Nested Comments Unbound enables unlimited “max-depth” and direct replies in nested (aka “threaded”) comments, and also allows for formatting the results for readability and sustained discussion.
Commenters at busy sites encounter the problem of comment threads that become unwieldy, either because a single column format makes tracking or joining a complex conversation effectively impossible, or because, after reaching the extreme far side of even a 10-level deep thread, comments revert to a single-column format, with reply-links disappearing. NCU substantially reduces this problem – preserving all reply-links and allowing for virtually unlimited depth – and also provides the potential for unique, more readable or convenient custom formatting of nested conversations.
Nested Comments Unbound (NCU) achieves this objective through several alterations to basic WordPress comments: First, it rewrites the “max_depth” setting so that all comments, regardless of depth, can receive replies. Second, it allows the site operator to set maximum depth in Settings/Discussion to numbers higher than the built-in limit of 10. Third, it adds formatting allowing a comment thread at whatever designated depth to turn back and, if necessary, continue “snaking” for as long as commenters care to continue it. Though the initial change already allows for a better “deep” discussion, the additional changes will help make the results easier to follow.
Nested Comments Unbound works with standard WordPress themes – including the vast majority available in the theme repository – but will most likely need to be adjusted for good results – or in some cases to produce any usable results at all. Commenting templates that vary substantially from standard WordPress can often also be adjusted, but there will be exceptions. See plugin documentation for further discussion, and for examples of ways to make an unbounded-nested thread stand out and be understandable and useful.
(A preliminary version of NCU implemented at Ordinary Times in 2015. The current version is in use at this site – as of February 2017.)