In SRFI 135, "text" means "immutable sequence of characters".  A mutable text would be a contradiction in terms.

On Tue, Aug 17, 2021 at 11:34 AM Marc Nieper-Wißkirchen <xxxxxx@gmail.com> wrote:

Am Di., 17. Aug. 2021 um 17:04 Uhr schrieb John Cowan <xxxxxx@ccil.org>:

I think the disjointness requirement only means that a string cannot be both mutable and a text, which is already true in Gauche.

Is such a requirement really important? If not, it should probably be dropped.