...If you accept that it's a generic Arabic greeting in a form of Arabic that's not used anywhere except in the Koran or formal situations, why are you bringing it up in a thread about Afghan culture?
It was primarily to show why you would never use a Muslim greeting in a toilet -because 'al-Salaam' / 'the Peace' is one of Allah's names.
The 'l' is assimilated, but without it there is no definite article so technically the greeting becomes "may peace be upon you" instead of "may the Peace be upon you". There's a massive difference between the two - at least to a Muslim, if not to you or @Mr_Pink. Understanding the difference doesn't depend on understanding the language, it depends on understanding the culture at its most basic.
@Mr_Pink felt he had to make a point to show off his 'expertise' - even though there was no point to be made as there is no "correct" way of writing 'al-Salaam' or 'a-Salaam' or 'as-Salamu', or 'al-Salamu' etc, unless you are writing strictly phonetically. Nobody was. Nobody has.
Since then its taken on a life of its own with others jumping on the bandwagon to show their similar 'expertise'. Only you, though, have displayed total ignorance.