OK, from the beginning. I wanted a BB code [code]..[/code], so when regular BB codes ([/b], [i][/i], etc.) are enclosed within the code BB code, they do not get encoded and are displayed as it is.

For example:
[code][b]Hi there[/code] will display Hi there and not Hi there

Ok... but what is purpose of it?

We've had previously 'Disable BB codes' checkbox and I guess its purpose is the same...

Ok... but what is purpose of it?

Some times, I need to explain the users on BB codes usage.

We've had previously 'Disable BB codes' checkbox and I guess its purpose is the same...

Yes, the purpose is same.

So you can just put this box back and it should work ;-)
In the core files there were no changes regarding it.

main_post_form template:

<input type="checkbox" name="disbbcode" value="on" />{$l_disableBbCode}

So you can just put this box back and it should work ;-)
In the core files there were no changes regarding it.

Oh thank you! I guessed the main core files were changed too :)