Influence is decided before the data
The diagonal of the hat matrix sums to the number of columns and the response appears nowhere in it, so a fit has exactly p units of influence to hand out among m observations. The same row at h = 0.5 is a ten-fold outlier on one design and a boundary case on another, and which of those it is was settled before a single measurement was taken.
rung 1 · leastsquares