[Lesane]

Figment, you could check the post if it contains [sig]. If so, then show "postbit_nosig" template.

To do so, open admin/functions.php and find:

PHP Code:

//highlight words for search engine 


Add above it:

PHP Code:

i$string_find="[sig]";
if(strstr($post[pagetext], $string_find)) {
eval("standarderror(\"".gettemplate('post_nosig')."\");");
} 


Then make a new template named post_nosig with the message that you don't allow the tag [sig] in any of the posts.