fix discussion comment styling

lms/static/sass/discussion/views/_thread.scss

@@ -80,10 +80,11 @@
 .discussion-comment {
   .response-body {
     @extend %t-copy-sub2;
+    @include padding(($baseline / 2), ($baseline * 1.5), 0, 0);
 
     display: inline-block;
-    margin-bottom: ($baseline/2);
-    width: flex-grid(10,12);
+    margin-top: ($baseline/2);
+    width: flex-grid(10, 12);
 
     p + p {
       margin-top: ($baseline/2);
@@ -95,7 +96,7 @@
     @include right($baseline / 2);
 
     position: absolute;
-    top: $baseline / 2;
+    top: 0;
   }
 }