No thats not it, the snap to grid is off. The offset does not seem to be aligned particularly to the grid. The screenshot attached shows an example of the problem. The first spline is a 4 point rectangle (corner visible) to which I tried to stitch in another spline to its edge. The green point in the picture is the height at which I clicked the rectangle. You can see though, that the point actually was added above where I clicked. Immediately after I added this point, I moved the mouse straight off to the left, creating a diagonal line. You can see that the point did not snap to any grid line, either. Is this a modeling setting that's gone wrong? A preference, perhaps?