Try adding the following code to your Free Nodelet Settings, and enable your Free Nodelet in Nodelet Settings. Then you'll have a link in your Free Nodelet that filters language on the current page when you clikc on it.

One could also set this to run after every page load, but note that this may break things, because it filters text inside script or style tags too.

<p>
<script type="text/javascript" defer><!--
function langfilter() {
function r(x) { if(Node.TEXT_NODE == x.nodeType){ var s=x.nodeValue; v
+ar n=s.replace(/\b(f)u(?:c)k/ig, function(c0,c1){return c1+"---"}); i
+f(s!=n){ x.nodeValue=n; } }; var t; if(t=x.firstChild)r(t); if(t=x.ne
+xtSibling)r(t); }; r(document.documentElement)
};
//--></script>
<a href="javascript:langfilter()">Watch your tongue!</a>
[download]

Below is some dirty words so that you can easily test that this feature works.