Collapsible comments allows the collapsing and expanding of commemnt threads through the use of jQuery. It helps improve usability and readability of the comment threads by removing the visual noise of deep threaded conversations.
Use case
You want to allow threaded comments (indented) replies, you have Threading enabled in the content type(s) comment options.
However, sometimes users reply to one another too many times, and the whole thing becomes a mess, both visualy and in terms of usability.
This module lets you handle that purely through the use of jQuery, by specifying up to what level of indentation to show, and collapse after that.
How it works
Collapsible comments adds a small js file (collapsible_comments.js) to every page load.
Note that the js file could be added only if there are comments in the page, but it would mean making your users have download different bundles of js files, and in the end hurting frontend performance.
How to use it
Simply install the module as usual. (doc)
Go to admin/config/content/collapsible_comments to configure the options.