How discard Lightweight markup language ? (Markdown, bbocde etc..)

[BobSquarePants]

Hi,

I've noticed that if a string contain some LML sometimes it get deleted, sometime not, depending of the string. Any ideas how to keep them for example:

input: This is a String with some [br] bbcode
expected output: Esta es una cuerda con un poco de código [br] bbcode

Thanks.