On 30/06/2014 09:22, Joseph Wright wrote:
>  - Brace groups/escaping: the current version takes an approach similar
>    to BibTeX, treating all brace groups as 'preserved'. This is a
>    clear rule but leaves open questions on how (if at all) to handle
>    commands in 'text'. Notably, these functions are intended for 'text
>    like' input, so this may not be an issue. Notice that math mode
>    is given no special treatment but can be protected from case
>    changing by bracing.
To be clear, the operations do not case-change command sequence tokens:
I was referring to commands with arguments, as the brace groups will
prevent any case change:

  \tl_upper_case:n { Some~\emph{text} } => "SOME~\emph{text}"
Joseph Wright