Welcome email sample shows differing text

This is for version 1.3.5.

When viewing the welcome email sample/preview in Admin > Email Welcome, you're given two separate samples at once - HTML and plain text.

After making a number of changes to the welcome email I noticed that one section of text was only showing up in the HTML sample, and not in the plain text sample. To find out why, I decided to remove all the text from languages/create_account.php and email_extras.php, however this section of text still remained (even though I removed it from the language files).

I performed a site-wide search for the words "This email address was given" (EMAIL_DISCLAIMER) and it found a match in the admin directory - admin/includes/languages/english/email_extras.php to be exact. Why is it coming from here when it's already in the catalog directory? Furthermore, why doesn't it display in the plain text sample?

It seems like a bug to me, but maybe it's by design.