as receiver of messages switch-off received notifications

It might or might not be possible to create a client that avoids/delays the acknowledgment of the receipt of messages.
Please see https://core.telegram.org/mtproto for the Telegram protocol details and how acknowledgments work.

This is not planned. Only Telegram Task Force uses such features. We implement the client in line with Telegram recommendations and the Android counterpart.

Having said that, the project is open source, so you're free to modify it. But please don't call this a privacy violation case, this is how a Telegram client is expected to work. Hence the "won't fix" status.

Of course it is a privacy violation case when a piece of software is
giving to others the information (without my permission) that I have
received a message on the screen. No matter if the propriety server of
Telegram (and FB and others) are expected to work so. Tomorrow someone will
perhaps say, software is expected to have back doors for NSA and so we
must implement this because it "is expected to work".

As you are unwilling to implement it at least as a configurable and as I'm
not in the knowledge to change and build it, my private state of this
piece of software goes along with your "Won't Fix" to

==> "Won't Use".

For the sake of documentation, I will include a link to the mailing list thread, where this matter has been elaborated on:

https://lists.launchpad.net/ubuntu-phone/msg14356.html

I agree with Mathias, this conceptually is the same as in return receipts in ordinary email; it is a feature implemented by Mail User Agents, and every (serious) Mail User Agent permits the user to disable it. If this feature is part of the Telegram protocol, the protocol itself is seriously broken, and in that case I will avoid at all Telegram usage.
MDNs (RFC 3798) are a formalization of "Return Receipts" for being processedby, but exactly for the same privacy reasons Mathias refers to, "requests for MDNs are entirely advisory in nature - i.e. recipients are free to ignore such requests": https://en.wikipedia.org/wiki/Return_receipt#Message_disposition_notifications

"In email, [...]" - that's how the article starts.
"This is in contrast with a physical delivery medium in which a courier acting on behalf of the sender can honor the sender's requirements for delivery" - minus the physical part, consider Telegram that courier, which defaults to requiring report of delivery for all senders. For most users, it's a feature, not a bug.

Folks, we can nitpick on this, but this really distracts me from working on second major revision of the app. I have reached out to Telegram, expect an official reply shortly.

Lastly, if Matthias is so concerned about privacy, why post your phone number to a public mailing list? (I'm not picking, just pointing out seeming lack of consistency in the matter you're pursing.)

Privacy means that I decide which information *I* want to share about *me*. If I decide to have my phone number in my signature that folks can reach me, this is my own decision. In the issue we are talking about, it is Telegram who makes the decision to share the information to the sender that the messages was read by me. Do you get the fundamental difference, Michał?

Sure, Matthias, I acknowledge that. Sit tight, I made sure TTF would reply to you, so at least you know it's not my decision, but an upstream one, and considered a feature more than a bug.

Telegram's support sent me a mail on July, 26. I can not copy it here due to the fact they have sent it only to me and Michał. They claime that their "read" status is an important advantage of the service over email and other message communications. It is in their opinion an integral feature of Telegram and they are unwilling to consider any change.

I replied to them:

Hello Telegram Support,

Thank you for your message.

No, I have not contacted <email address hidden> by email, but using the web form
https://telegram.org/support

Please consider reading this bug report in bugs.launchpad.net to get a
full picture about the issue we are talking:

https://bugs.launchpad.net/libqtelegram/+bug/1475915

Please be so kind and make your Comment there. Or Michał Karnicki or I
could make a summary of your statement there. I'd prefer that you do it.

Finally, I will not hide, that I'm very disappointed about the style of
your answer, an answer without taking into account that some potential user of
your service sees a violation of privacy, implemented by Telegram.

Kind Regards

Matthias

There is a solution: installing the (unoficional) Telegram client "telegram-cli" in the BQ and here is how this goes:

http://www.unixarea.de/bq/bq-aquaris-e45-ubuntu.txt

31. Compiling the Telegram client "telegram-cli" in the jail

    How to compile telegram-cli directly on the BQ. Make sure you
    have in the above constructed jail (see chap. 30) a working gcc:

    # apt-get update
    # apt-get install install gcc libc6-dev

    Download the sources with 'git', and install its dependency. The required
    Python does not match the installed version:

    # apt-get install git
    # apt-get install libreadline-dev libconfig-dev libssl-dev
    # apt-get install lua5.2 liblua5.2-dev libevent-dev libjansson-dev make
    $ git clone --recursive https://github.com/vysheng/tg.git
    $ cd tg
    $ ./configure --disable-python
    ...
    $ sudo mkdir /etc/telegram-cli
    $ sudo cp server.pub /etc/telegram-cli
    $ cp telegram-cli ..

    $ ~/telegram-cli
    Telegram-cli version 1.3.3, Copyright (C) 2013-2015 Vitaly Valtman
    Telegram-cli comes with ABSOLUTELY NO WARRANTY; for details type `show_license'.
    This is free software, and you are welcome to redistribute it
    under certain conditions; type `show_license' for details.
    Telegram-cli uses libtgl version 2.0.3
    Telegram-cli includes software developed by the OpenSSL Project
    for use in the OpenSSL Toolkit. (http://www.openssl.org/)
    I: config dir=[/home/phablet/.telegram-cli]
    > contact_list
    Emil Apitz
    ...

    Now Emil sends a message from his mobile 'Got it?' which arrives in telegram-cli
    and I replied with 'ok'

    [12:17] Emil Apitz >>> Got it?
    > msg Emil_Apitz ok
    [12:18] Emil Apitz <<< ok
    User Emil Apitz marked read 1 outbox and 0 inbox messages

    Note: The user Emit sent the message 'Got it?' and I received it with
    the Telegram client telegram-cli, and read it, but it stays in the
    device of Emil with only one single marker 'v'. This is what we wanted to have
    as PRIVACY.

Hi all,

In a private conversation with Matthias I said I hoped we would revisit this matter when Telegram 2.x was out. Now that it happened, and this bug report has been brought again to my attention, we have reviewed it. We have a solution that I believe would satisfy the requirements set by the bug description.

The proposed solution is the following:
The application may provide a setting to turn off "send message read notifications for received messages". The user who chooses to do that will in turn not see "message read notifications for sent messages". I think it is fair and that is a solution we are happy to go ahead with.

While we will do our best to continue maintaining and hopefully growing Telegram for Ubuntu, we are currently short on cycles. Therefore, we would be more than happy to accept a merge proposal with this feature, we simply can't commit to it at the moment as there are more higher priority bugs right now. But I am changing the bug status from "Won't fix" right now.