Screw reply navigation, there are top and bottom links on 4chan itself. Also return guard.

4chan_x.user.js

@@ -60,7 +60,6 @@
         'Comment Expansion': [true, 'Can expand too long comments.'],
         'Thread Expansion': [true, 'Can expand threads to view all replies.'],
         'Index Navigation': [false, 'Navigate to previous / next thread.'],
-        'Reply Navigation': [false, 'Navigate to top / bottom of thread.'],
         'Check for Updates': [true, 'Check for updated versions of 4chan X Alpha.']
       },
       Filtering: {
@@ -2237,6 +2236,9 @@
   Nav = {
     init: function() {
       var next, prev, span;
+      if (g.VIEW !== 'index' || !Conf['Index Navigation']) {
+        return;
+      }
       span = $.el('span', {
         id: 'navlinks'
       });
@@ -2256,18 +2258,10 @@
       });
     },
     prev: function() {
-      if (g.VIEW === 'thread') {
+      return Nav.scroll(-1);
-        return window.scrollTo(0, 0);
-      } else {
-        return Nav.scroll(-1);
-      }
     },
     next: function() {
-      if (g.VIEW === 'thread') {
+      return Nav.scroll(+1);
-        return window.scrollTo(0, d.body.scrollHeight);
-      } else {
-        return Nav.scroll(+1);
-      }
     },
     getThread: function(full) {
       var headRect, i, rect, thread, threads, topMargin, _i, _len;
@@ -6153,7 +6147,7 @@
       initFeature('Thread Stats', ThreadStats);
       initFeature('Thread Updater', ThreadUpdater);
       initFeature('Thread Watcher', ThreadWatcher);
-      initFeature('Index/Reply Navigation', Nav);
+      initFeature('Index Navigation', Nav);
       console.timeEnd('All initializations');
       $.on(d, '4chanMainInit', Main.initStyle);
       return $.ready(Main.initReady);

src/config.coffee

@@ -10,7 +10,6 @@ Config =
       'Comment Expansion':            [true,  'Can expand too long comments.']
       'Thread Expansion':             [true,  'Can expand threads to view all replies.']
       'Index Navigation':             [false, 'Navigate to previous / next thread.']
-      'Reply Navigation':             [false, 'Navigate to top / bottom of thread.']
       'Check for Updates':            [true,  'Check for updated versions of <%= meta.name %>.']
     Filtering:
       'Anonymize':                    [false, 'Turn everyone Anonymous.']

src/features.coffee

@@ -1027,6 +1027,8 @@ ArchiveLink =
 
 Nav =
   init: ->
+    return if g.VIEW isnt 'index' or !Conf['Index Navigation']
+
     span = $.el 'span',
       id: 'navlinks'
     prev = $.el 'a',
@@ -1043,16 +1045,10 @@ Nav =
     $.on d, '4chanXInitFinished', -> $.add d.body, span
 
   prev: ->
-    if g.VIEW is 'thread'
+    Nav.scroll -1
-      window.scrollTo 0, 0
-    else
-      Nav.scroll -1
 
   next: ->
-    if g.VIEW is 'thread'
+    Nav.scroll +1
-      window.scrollTo 0, d.body.scrollHeight
-    else
-      Nav.scroll +1
 
   getThread: (full) ->
     headRect  = $.id('header-bar').getBoundingClientRect()

src/main.coffee

@@ -344,7 +344,7 @@ Main =
     initFeature 'Thread Stats',             ThreadStats
     initFeature 'Thread Updater',           ThreadUpdater
     initFeature 'Thread Watcher',           ThreadWatcher
-    initFeature 'Index/Reply Navigation',   Nav
+    initFeature 'Index Navigation',         Nav
     console.timeEnd 'All initializations'
 
     $.on d, '4chanMainInit', Main.initStyle