Topic: my polylines have way too many segments!

[Dinosaur]

It still sounds like a product of importing a vertical app's object into an autoCAD primitive.  If those polylines were once part of some "smart object" there can be a lot of excess baggage along for the ride.  If those ploylines had been generated by the vertical utilizing the REGION or BPOLY command, you would find a polyline with vertices at every point of intersection by other linework along the resulting boundary once it is exploded out of the original object.

[jonesy]

Having worked with verticals in the past, I can certainly see how that can happen, but, for example on one window frame there "should" be one grip for each corner of the window, being that all it is is a rectangle, with no change of shape/direction etc. This rectangle has about 20 grips along each segment, and I get no proxy messages, and no incompatibility messages. The drawing, as far as I am aware, has never been part of a 3d model. I can honestly say that I have never seen this behaviour in a drawing before.

[Dinosaur]

That is what happens when a polyline is generated with BPOLY or REGION commands - any line that intersets the bounding polyline will create a vertex at that point even if it is on a continuous course.  Think of all the little parts created in a window or door object and all of the potential intersections.