If a user leaves a comment with a link, the domain of the first link is added to the beginning of the comment.
For example, a user leaves a comment with a link:
Hey! Great article. I wrote one very similar.
When the comment is published it shows up like this:
example.comHey! Great article. I wrote one very similar.
If I try to edit out the offending text from within WP, it reappears afterward. I am only able to get rid of the text by editing the comment in phpMyAdmin.