I was using:
.fb-comments, .fb-comments span, .fb-comments iframe[style] {
width: 100% !important;
}
To make Facebook Comments responsi
I had the same issue (implemented the responsive comments yesterday, today it didn't work anymore ).
I don't have enough points to vote but the above answer works. I am using the facebook plugin for wordpress. I also set a timeout when the page loads to get the right width immediately.
setTimeout(function(){
$(".fb-comments").attr("data-width", $(".comments-area").width());
FB.XFBML.parse($(".comments-area")[0]);
}, 1000)