this setting should disable all the nag messages

src/General/Config.coffee

@@ -95,7 +95,7 @@ Config =
       ]
       'Show Support Message': [
         true
-        'Warn if your browser is unsupported. 4chan X may not operate correctly on unsupported browser versions.'
+        'Warn if your browser or configuration is unsupported and may cause 4chan X to not operate correctly.'
       ]
 
     'Linkification':

src/General/Main.coffee

@@ -142,10 +142,11 @@ Main =
     else
       $.event '4chanXInitFinished'
 
+    return unless Conf['Show Support Message']
     <% if (type === 'userscript') { %>
     test = $.el 'span'
     test.classList.add 'a', 'b'
-    if test.className isnt 'a b' and Conf['Show Support Message']
+    if test.className isnt 'a b'
       new Notice 'warning', "Your version of Firefox is outdated (v<%= meta.min.firefox %> minimum) and <%= meta.name %> may not operate correctly.", 30
 
     GMver = GM_info.version.split '.'