CODE
<$MTEntryTitle encode_url="1">


In dynamic mode provides output like this:
CODE
my+entry+title

In static mode it provides output like this:
CODE
my%20entry%20title


The fix is to change modifier.encode_url.php:
CODE
return urlencode($text);

It should read:
CODE
return rawurlencode($text);


That should provide proper RFC1738 URL encoding according to the PHP documentation.