Scott Nelle

WordPress lets you set a number of days after which comments will be unavailable for individual posts. This plugin will allow you to keep commenting open on specific posts.
Once the plugin is enabled:
<ul>
<li>Set a comment deadline in Settings > Discussion using the “Automatically Close Comments…” option. Closing comments on old posts is a great way to avoid spam comments.</li>
<li>Edit an individual post on which you’d like to keep discussion open indefinitely and check the Override Comment Deadline box.</li>
</ul>

Override Comment Deadline

Allows you to enable comments on posts which are older than the comment deadline set in discussion settings.

Robin W

Pascal Casier

Adds an option to the Discussion meta box to use a bbPress topic instead of WordPress comments, and displays that topic beneath the post on your site.
You can let the plugin create a new topic for you in the forum of your choice, or specify an existing topic to attach to the post. 
A topic can be attached to as many posts as you’d like, but only one topic can currently be attached to a post.

Post Comments as bbPress Topics

Great support!

I use it to link my Learndash to bbpress forums so that my students can discuss a lesson, either under it or in a forum topic. Really practical, glad that this plugin exists!

Really practical, glad that this plugin exists!

Replace the comments on your WordPress blog posts with topics from an integrated bbPress install

Override Comment Deadline vs Post Comments as bbPress Topics