Thanks for taking this seriously. I hope you grasp how really deeply ingrained this problem is.
The real problem is the lack of good quality control. If Rhino had good quality control when a serious malfunction gets introduced it would be noticed immediately and fixed immediately. It would not linger in the code for years and years and lead to further malfunctions.
The thread where I first posted about this problem with Rhino7 edges has a model that illustrates perfectly what I’m talking about.
Here is the same model with clear instructions on how to reproduce the problem. Bogus_Edges.3dm (129.1 KB)
In this file you will find a cyan polysurface which you trim with a red curve.
After trimming with the red curve run the DupBorder command and it tells you that it produced 3 borders.
WTF!
How is that even possible? How is it possible to cut off a part of polysurface with one curve and turn the object with one border into an object with 3 disconnected borders? Two of the so-called borders are just tiny little lines.
And of corse Check command tells you its a valid polysurface
The last time Rhino was able to trim the cyan polysurface with the red curve was Rhino5. So it looks like this bogus trimming strategy was introduced 7 or 8 years ago and has been plaguing Rhino users ever since.
And that brings us to the topic of this thread…
How is it possible for the edges of a Brep to not have their end points at the Brep’s vertices? How is that obviously invalid construct even allowed to exist?