Hi Berube, that's a "curve bleed thru" type of display artifact, it's not really related to viewport clipping, it's a side effect of trying to prevent an even worse artifact of "curve stippling". That's where curves and edges would be partially hidden by the surfaces they are on. To avoid curve stippling the display engine pulls curves and edges forwards in depth before drawing them so that won't get stippled.

Check out this previous thread for some more information:
http://moi3d.com/forum/index.php?webtag=MOI&msg=8194.2

- Michael