Make 'Threading' and 'Show Last <n>' checkboxes turn each other off.

src/General/Config.coffee

@@ -407,7 +407,7 @@ Config =
       ]
       'Reply Pruning': [
         true
-        'Hide old replies in long threads. Number of replies shown can be set from header menu. Not compatible with Quote Threading.'
+        'Hide old replies in long threads. Number of replies shown can be set from header menu.'
       ]
 
     'Posting and Captchas':

src/Monitoring/ReplyPruning.coffee

@@ -1,6 +1,10 @@
 ReplyPruning =
   init: ->
-    return unless g.VIEW is 'thread' and Conf['Reply Pruning'] and not Conf['Quote Threading']
+    return unless g.VIEW is 'thread' and Conf['Reply Pruning']
+
+    if Conf['Quote Threading'] and Conf['Thread Quotes'] and Conf['Prune Replies']
+      Conf['Prune Replies'] = false
+      $.set 'Prune Replies', false
 
     @container = $.frag()
 
@@ -15,7 +19,7 @@ ReplyPruning =
       enabled: label.firstElementChild
       replies: el.lastElementChild
 
-    $.on @inputs.enabled, 'change', $.cb.checked
+    $.on @inputs.enabled, 'change', @setEnabled
     $.on @inputs.replies, 'change', $.cb.value
 
     Header.menu.addEntry
@@ -30,6 +34,13 @@ ReplyPruning =
   hidden: 0
   total: 0
 
+  setEnabled: ->
+    other = QuoteThreading.input
+    if @checked and other?.checked
+      other.checked = false
+      $.event 'change', null, other
+    $.cb.checked.call @
+
   node: ->
     ReplyPruning.thread = @
     ReplyPruning.total = @posts.keys.length - 1

src/Quotelinks/QuoteThreading.coffee

@@ -17,7 +17,7 @@ QuoteThreading =
     @input = $('input', @controls)
     @input.checked = Conf['Thread Quotes']
 
-    $.on @input, 'change', $.cb.checked
+    $.on @input, 'change', @setEnabled
     $.on @input, 'change', @rethread
     $.on @threadNewLink.firstElementChild, 'click', @rethread
     $.on d, '4chanXInitFinished', => @ready = true
@@ -38,6 +38,13 @@ QuoteThreading =
   children: {}
   inserted: {}
 
+  setEnabled: ->
+    other = ReplyPruning.inputs?.enabled
+    if @checked and other?.checked
+      other.checked = false
+      $.event 'change', null, other
+    $.cb.checked.call @
+
   setThread: ->
     QuoteThreading.thread = @
     $.asap (-> !Conf['Thread Updater'] or $ '.navLinksBot > .updatelink'), ->