You can modify this. Check inside of template-functions-post.php. I wrote a bit about it here:
I only post the link because it might be a helpful one to modify this quicktag. Let me know if that helps you out. I didn't mention this modification specifically (yet), but I did do it, so I know that what I mention on that page is close to where you make the changes for it to display a BR tag or not.
I didn't like the BR tag either, as that tag is set to be phased out anyhow. I replaced that BR with a <p class="more_link"> and I set the padding how I wanted it on that paragraph break, instead of the BR tag.