For one thing, BBM breaks VaultWiki tags. For some reason I can't understand, it clears the object callback for BB-Code tags. I guess it figures BB-Codes will only be created through BBM, but this isn't compatibility minded. The problematic code is in
library/BBM/BbCode/Formatter/Base.php. It might be in other formatters too:
Code:
if(isset($tagInfo['callback'][0]))
{
$tagInfo['callback'][0] = '';//Not needed for info (recursive)
}
This breaks the reference to the class that knows how to parse wiki BB-Codes. I think it should have a method in place to determine if the tag was created by BBM before making such dramatic changes to the tag's definition. If it is clearing it for memory purposes, that's unnecessary. The value is either a string, with very small footprint, or an object reference. In PHP 5, it is not a clone object, but a reference to the same internal pointer for the object, so again, very small footprint.
Currently, because of these lines, the page will simply crash if a wiki BB-Code is used. If I comment out the above lines from BBM, the page doesn't crash and the wiki BB-Codes parse as expected. As far as I can tell, BBM still functions as expected too.
This might be the cause of your issue. Please check with BBM's author for a solution, then do your tests with the [category] tag again.
By the way, my entire test assumes you made a wiki Prefix named 'Category' (or similar) that has the BB-Code 'category' in its settings. If you are using another method to create wiki tags (and you don't want to use the WIKI tag for some reason) please let me know.