Remove obsolete IE8 opacity hacks; remove unused transparency mixin.

app/assets/javascripts/notes.js

@@ -13,9 +13,6 @@ Danbooru.Note = {
 
       $inner_border.css({
         opacity: opacity,
-        "-ms-filter": "progid:DXImageTransform.Microsoft.Alpha(Opacity=50)",
-        "filter": "alpha(opacity=50)",
-        zoom: 1
       });
 
       var $note_box = $('<div/>');

app/assets/stylesheets/common/000_vars.css.scss

@@ -49,13 +49,6 @@ $preview_flagged_color: #F00;
   text-shadow: $val;
 }
 
-@mixin transparency($value) {
-  opacity: $value;
-  -ms-filter: unqoute("progid:DXImageTransform.Microsoft.Alpha(Opacity=#{$value * 100})");
-  filter: unquote("alpha(opacity=#{$value * 100})");
-  zoom: 1;
-}
-
 @mixin inline-block {
   display: -moz-inline-box;
   -moz-box-orient: vertical;

app/assets/stylesheets/specific/comments.css.scss

@@ -41,16 +41,10 @@ div.comments-for-post {
     }
 
     article.comment.below-threshold {
-      -ms-filter: progid:DXImageTransform.Microsoft.Alpha(Opacity=30);
-      filter: alpha(opacity=30);
-      zoom: 1;
       opacity: 0.3;
     }
 
     article.comment.below-threshold:hover {
-      -ms-filter: progid:DXImageTransform.Microsoft.Alpha(Opacity=100);
-      filter: alpha(opacity=100);
-      zoom: 1;
       opacity: 1.0;
     }
   }