You can control icons direction using the following CSS:
[dir=ltr].fa-dir-flip .fa.fa-flip-horizontal,
[dir=rtl].fa-dir-flip .fa,
[dir=rtl] .fa.fa-dir-flip {
filter: progid:DXImageTransform.Microsoft.BasicImage(rotation=0, mirror=1);
-webkit-transform: scale(-1, 1);
-ms-transform: scale(-1, 1);
transform: scale(-1, 1);