Kat Hagan

This plugin allows you to selectively disable comments for visitors from certain sites (e.g. reddit). If a visitor’s HTTP referer matches one of the hosts you’ve blacklisted, your post will look as if comments have been disabled (neither existing comments nor the new comment form will be shown).

Disable Comments By Referer

Ban visitors from certain sites from viewing or adding comments.

ilanco

Hide Referer for WordPress removes the referer (referrer) from all external links on your blog. It does this by converting all outgoing 
links on your blog using the unrefer.com service and effectively hides your site as origin of the referred link.
For example, Hide Referer for WordPress will convert an external link to wordpress.com, to <a href="http://unrefer.com/?http://wordpress.org" rel="nofollow ugc">http://unrefer.com/?http://wordpress.org</a>.

WordPress Hide Referer

Test

Hide your referer (referrer) on all external links with unrefer.com.

Disable Comments By Referer vs WordPress Hide Referer