Raven’s antispam – powerful and invisible fighter against comment spam. No set-up necessary, install and forget.
<h4>Details</h4>
Visitors with enabled JavaScript (99%+) see nothing – no annoying questions, no captcha, nothing. (Users with disabled JS see an additional text-field and a word that must be rewritten into the textfield.)
Note: this plugin is not able to check your trackbacks – to handle trackback spam, it’s necessary to use some other solution. (I recommend to disable trackbacks globally, since they rarely bring any benefit for your readers.) <a href="http://kahi.cz/wordpress/ravens-antispam-plugin/" rel="nofollow ugc">more…</a>.

Raven's Antispam

Powerful and invisible fighter against comment spam.

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

Raven's Antispam vs Post Comments as bbPress Topics