The common error with blindness and such is people tend
to think that blind and non-blind are a lot different.
They are not.
Interesting you should presume I (we) lack experience with
blind people, as a matter of fact I have socialized, worked,
and performed music with people who happened to be blind.
I presumed your lack of understanding, not experience.
Just as an Australian non-blind can read en-us mails
without content language information, an Australian
blind can recognize it without content language
Ah, but the agent doing the reading for the Australian-blind
would be able to use the content language information if it
were present, and IMHO the agent will need it for technical reasons.
Wrong. What the reading agent needs is what a non-blind mail recipient
needs. Nothing more or less than that. Also, whether the reading agent
is human or not does not matter.
So, what you should have done is not to overly worry about blinds
but to show non-blind readers needs detailed content language
information, which is unlikely though.
You can better understand the issue by considering the case with
more distant dialects such as Mandalin and Cantonese, users of which
can not orally communicate.