"Disable BB Code Within This BB Code" not working?

[catechu]

(I'm using vBulletin 3.8.4, Patch Level 1.)

I've created a custom BB Code, "python", which is supposed to expand to

[highlight=Python]{param}[/highlight]

and then be parsed into a code block in the post.

This highlighting is done with a Product, and works perfectly when I enter the expanded tags manually into the window. For example, entering:

[highlight=Python]import sys[/highlight]

is properly outputted as a code block, but entering:

[python]import sys[/python]

is outputted as the plain text with naked BB Code:

[highlight=Python]import sys[/highlight]

and not as a code block.

Now, my first thought was that I had accidentally disabled BB Code within custom BB codes, but this is not the case -- I've set it to "No." I've also tried the same thing with the bold tag, and it outputs the naked BB Code there as well, instead of boldface text. I've attached the settings for this custom BB Code.

Am I missing something obvious? I've reached my wits' end.

Thanks!

[catechu]

Any suggestions? I haven't been able to figure this out since I posted.

[Zachery]

The bbcode parser was not designed to parse bbcode used inside of its replacement text.

[catechu]

Hmm...clicking on the question mark next to the option seemed to imply that one could (e.g. with bold tags), so I got confused. Thanks for the clarification!