A Revealing Note

This seems to have come up fairly often so I should probably address it in a post. Every now and then, a בעל קריאה will mix up תְגַלֶּה (with a סגול) and תְגַלֵּה (with a צירי.) This comes up many times in אחרי מות and again in קדושים as well. I have seen people get rather antsy about this. However, (please correct me if I'm wrong) there is absolutely no difference whatsoever. The only factor that determines the נקוד under the ל is that it will get a צירי if it is at the end of a פסוק or on an אתנחתא. Otherwise, it will be a סגול. This should never be corrected by anyone on the spot.

סוכת דוד

I'm sure everyone will notice the reference in this week's הפטרה to the phrase we insert in ברכת המזון for סוכות - (actually, it's the other way around, the phrase is a reference to the פסוק)

הרחמן הוא יקים לנו את סכת דויד הנופלת

I'm probably not the only one, however, to notice the slight anomaly in the פסוק. We are accustomed to saying הַנֹּפָלֶת, with a קמץ under the פ. I believe it is this way in most, if not all ברכונים. But in the עמוס ט:י"א ,פסוק, it is written with a סגול, even though it is on an אתנחתא.
This therefore begs two questions:

1. Why would it not change to הַנֹּפָלֶת on an אתנחתא?
2. Seeing as it does not in the original biblical text, why would we change it in ברכת המזון?
   
   
   Please see Elie's comment.