"DelDupVertex.fas deletes duplicate polyline vertices. It is intended to eliminate vertices that are so close they are indistinguishable. But tolerance setting can be any value and even visibly distinct vertices can be eliminated. Only new style, "lightweight" polylines are supported, not old style polylines.
Notes from Cadalyst Tip Patrol: Polylines are very useful objects. Sometimes vertices can get a little crazy for one reason or another. This routine will delete vertices whose distance falls inside the tolerance you provide. The default tolerance is so small that it will delete vertices that are on top of each other or very close. If you want to get rid of vertices that are five units apart, set the tolerance to 5. The routine will delete one of the two vertices. This is a nice routine if you are trying to hatch a closed polyline, but can’t because vertices are on top of each other and you can’t figure out where they are. This routine could help.