@Arsalan
I'm sorry for the delay. Looks like I made a stupid mistake that messed up the whole site for me.
I re-installed OSSN again and added the RTL version 2.0 and enabled it.
Indeed, it works fine. Thank you very much.
If ever a formatting toolbar will be available in the future, would be very much appreciated.
Have a good time and thank you again.

@Did you followed me comment and used version 2.0 of RTL? It does exactly you saying. When you type Arabic it will make your text appear on right side during typing (comments and wall posts typing only).

Now please answer did you tried 2.0 and deleted old version before installing 2.0 version?

It's no rocket science - there's was simply no demand for a feature like that up to now as far as I know.
Feel free, Fikri, to develop that switchable aligner - every Ossn contributor is welcome!

Looks like I was not clear from the beginning.
Nothing to do with device or OS
Arabic text in comments and messages should be right aligned. Looks like this is not possible in OSSN so far.
All would be easy like butter if we had formatting toolbar, like we have here, or even a bit better.
Why is this rocket science in the 21st century? That's beyond my comprehension.
That's all.
Thank you.

Just in order to clear things up again:
The available language packs are meant to make static Ossn site elements (e.g. buttons, menus, table headers, etc.) appear in the language which has been chosen on the account settings page. That's all.

The available language packs don't have any impact on the character set currently in use for input. That is, if you want to switch from Arabic to Cyrillic or any other character set, you have to change the language of your device.

The instructions just say:

In opposite to components, Ossn language packs have to be installed manually with a file transfer utility of your choice.
un-zip the language pack on your local PC
start your file transfer utility
navigate to the language pack's directories on the left and your Ossn installation on the right
copy the 3 local directories on the left side to your server on the right

Apart from the fact that there are two directories not three, the instructions seem to be meant for a complete Arabization of the site altogether, which is not what I wanted.
I tried to copy the corresponding arabic .php files in the locale of all the components folders respectively, but nothing changed. How would it change if no option is provided for choosing language in comments or messages anyway.
I guess at this point I just give up and apologize for any inconvenience. Thank you for your patience.

I hope you have read the documentation about language packs installations https://www.opensource-socialnetwork.org/wiki/view/1988/how-to-install-language-packs

Arabic language is not installed because it is not compatible with current version 5.0 I have of OSSN
It fails to upload
and I don't want menus in Arabic anyway. All I want is to be able to write Arabic right aligned in posts, replies and chat.

Arabic language is not installed because it is not compatible with current version 5.0 I have of OSSN
and I don't want menus in Arabic anyway. All I want is to be able to write Arabic right aligned in posts, replies and chat.
+ I don't see when to activate RTL, sorry.

Try 2.0 it will not effect ltr language and will allow your users to use multi langues on same page.