As a user, I'd like to be able to visually identify which surfaces or lines belong to the model beeing edited or to a primitive/subpart (different coloring of surfaces/lines?). Currently it's confusing as you can select a surface or line from a primitive, try to modify it with no action, or duplicate it without knowing.
And a very, very tiny bug report: if you split a distance meter you get two normal edge lines instead of two distance meters.
And a very, very tiny bug report: if you split a distance meter you get two normal edge lines instead of two distance meters.