In light of this answer, why do we say V'imru amen and V'nomar amen at various points in bentching and davening when saying that passage alone? (eg. bentching by yourself, or oseh shalom at the end of ...
In Bentching by the end of the Harachamon's we say וְנאמַר אָמֵן and at the end of Magdil we say ואמרוּ אָמֵן. Is there a difference? What is the difference? Why the difference?