Delete the verts which has only two edges,regardless of their angels.
Delete the verts which has only two edges,but that verts which angel is smaller than threshold value will be ignore.
SnapZ | ZMove |SnapToP
Snap a point and set all z coordinates of selected vertices to z value of the point coordinates.
Snap two points ,move selected vertices in Z-AXIS from first point to second one.
Snap two points as direction, which the selected verts will move along on moving mouse.
One by one make each of selected edges flat.
One by one ,make each selected edge perpendicular to an arbitrary adjcent edge.
Clear these co-plane edges which can cause visual chaos.
Find extreme narrow polygons and select them.
Select those vertices that make surface looks dark.