That ID is added there so your readers can read the message that is displayed in the Blog Subscription widget:
"An email was just sent to confirm your subscription. Please find the email now and click activate to start subscribing."
If they were redirected to the top of the page, they might not know that they have to perform one additional step before to be subscribed.
Still, if you'd like to remove this ID from your URLs, you should be able to set up a redirect rule in your site's .htaccess file.