Hi Brian, I'll see if I can get the Intersect command to weed out duplicate intersections. For the current version I guess you would need your script to do that itself.

re:
> I have always thought that a re-Joined curve was the same as the initial single curve, but there must be some difference?
> So the curve "remembers" is former segments, unless Rebuild is used?

Yes Join on curves will generate a parent curve that has a list of head to tail segments in it. It doesn't automatically merge segments together. So if you use Edit > Separate on it it should break apart into the same pieces you had before using Join.

In v5 you can use the Merge command on it to merge segments that meet smoothly into longer segments.

- Michael