<p dir="auto">It's okay on Chrome 36 and on IE 11, sadly, it's pushing content to the left on Firefox 32.0, when you minimize the screen, then open the modal while it's minimized, then you maximize and open the modal again.</p>
<p dir="auto">div.input-append is a block that contains only floating elements, thus gets a 0px height; if a .help-block follows the div.input-append, it is displayed next to the div.input-append instead of under it, because the 0px-height div.input-append does not offset it vertically. adding "clear: left" to the .help-block seems to correct this problem, but I'm not sure if that won't break something else.</p>