| You can only format printable things...

Why?

Suppose I have

\2331;2RLorem ipsum dolor sit amet, consectetaur adipisicing elit, sed do
eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad
minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip
ex ea commodo consequat. Duis aute irure dolor in reprehenderit in
voluptate velit esse cillum dolore eu fugiat nulla pariatur.  Excepteur
sint occaecat cupidatat non proident, sunt in culpa qui officia

and run it through "fmt -60" I want to get:

\2331;2rLorem ipsum dolor sit amet, consectetaur
adipisicing elit, sed do eiusmod tempor
incididunt ut labore et dolore magna aliqua. Ut
enim ad minim veniam, quis nostrud exercitation
ullamco laboris nisi ut aliquip ex ea commodo
consequat. Duis aute irure dolor in reprehenderit
in voluptate velit esse cillum dolore eu fugiat
nulla pariatur.  Excepteur sint occaecat
cupidatat non proident, sunt in culpa qui officia

not something starting with "\0331;2r" which would be an invalid escape
sequence. (\233 aka CSI is the 8-bit equivalent of ESC [ on DEC vt
terminals).

Explani why this should not be permitted, and what it breaks to support it?

--jhawk