Hi Burt
Wordpress determine the content in the shortcode by the first end tag. For example,

[a]hello [a]world[/a] another[/a]

the first a shortcode end with the first [/a].  The result is the right string will not be considered a shortcode.

So the issue with columns is that one cannot nest columns of the same type as per your example.  We do not know a way to get around this by php as this is how WP behaves as a core function.

But you can try use

content

if it turns out you really need to nest (and are not just testing to find holes!)

I think this matter has come up once or twice on the forum in the past as well.

So an example would be:

Powerful Admin Panels

Morbi in sem quis dui placerat ornare. Pellentesque odio nisi, euismod in, pharetra a, ultricies in, diam. Sed arcu. Cras consequat. Vivamus magna. Cras in mi at felis aliquet.

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