Try this plugin:
https://github.com/NoahY/q2a-comment-collapse
More info here:
http://www.question2answer.org/qa/10493/collapsing-comments-plugin
Welcome to the Q&A site for Question2Answer.
If you have a question about Q2A, please ask here, in English.
To report a bug, please create a new issue on Github or ask a question here with the bug tag.
If you just want to try Q2A, please use the demo site.