Custom BB Code Nesting

I created a new custom BB Code for off topic comments, [ot]. It seems that the BB Code parser doesn't keep track of the level of a bb code tag, and it ruins the look of the post. This is a problem especially when quoting someone that has used the [ot] tag and then trying to put that inside another [ot] tag:

[ot]

[ot]Something off topic[/ot]

Something else off topic[/ot]

The parser would interpret lines 1-3 of that as the custom BB code, and screw up the formatting on it because of this (the quote tags would mismatch, and so would the last [ot]). It seems the parser doesn't take into account that another [ot] tag is open, and that it is in fact 2 levels deep.

Nesting quote tags works fine however, which leads me to suspect it is a problem with custom BB Codes only, but I could be wrong. I haven't looked at any of the code to verify any of this information.

For reference, the [ot] tag is defined as follows:

[ot]

{TEXT}[/ot]

...is replaced with...

<div style="margin: .5em 1px 0 25px; border: 1px solid #ff9999; background-color: #fff5f5; padding: 5px;">
<p style="font-weight: bold; font-size: .9em; ">Off Topic:</p>
{TEXT}

</div>

Maybe a new token could be made for text that may include other bb code?