Alright, after digging around some more on my own, I found it. It was, indeed, in the PHP code, not a phrase.
Open up
class_mail.php and search for this line:
Code:
$mailfromname = "$username @ " . $vbulletin->options['bbtitle'];
change it to
Code:
$mailfromname = "$username";
That did it.
Thanks for trying to help, but ya'll were just way off base with this one. If nothing else, your insistence that I look in phrases at least gave me the idea to use phrase variable names as a way to search through the PHP code, using Super Text Search, and then look for the offending bits of code.
--------------- Added [DATE]1234684026[/DATE] at [TIME]1234684026[/TIME] ---------------
To DISMOUNTED: Yeah -- there you go -- that was it. In a round-about way you did help me. I found it about 5 minutes ago, just before you wrote up your post.