Ihor Radchenko <yantar92@posteo.net> writes:

>>   #+BEGIN_SRC emacs-lisp
>>   (list (list 1 2) (list "/" "<>") 'hline (list 3 4) (list 5 6))
>>   #+END_SRC
>>
>> Org Babel outputs
>> ...
>> with the second element of the list
>>
>>   (list "/" "<>")
>>
>> swallowed, without a word.
>>
>> Why would Org Babel do this?
>>
>> And, how can one output tables with column groups?
>
> This is because of how `orgtbl-to-generic' is implemented. It is taking
> pieces from the full ox.el exporter, hard-coding certain things. For
> example, it always removes special table lines:
>
>     ;; Since we are going to export using a low-level mechanism,
>     ;; ignore special column and special rows manually.

I refactored `orgtbl-to-generic', so that it does not have to duplicate
`org-export-as'. Now, things should be more consistent with the normal
export.

May you try the attached tentative patch set?