As a complement to this question on Shortened Birkat Hamazon, I would like to better understand the practice I saw of stopping Birkat Hamazon after the fourth blessing on Shabbat and not saying the Harachamans and the closing text.
I believe it comes from the idea one should not make specific asks on Shabbat although others are saying that asks as part of an organized prayer are all right.
Where is this custom coming from?
How widepread is it?
Are there communities where it is the norm and rabbanim supporting it?