Welcome to the forum Bulldog!
The term "sugaring" that I'm familliar with describes unshielded melt thru on stainless steel welds. Sugaring often occurs when stainless pipes are purged improperly and the visible appearence is black, rough and grainey...definately unacceptable.
I'm not really getting a clear mental picture by your description. When you say "vibroscribe around the weld" are you talking about a shiney thin line along the toes of the weld, that might be a very thin margin of undercut?
Anyhow.. tell us a little more about what your encountering, lots of folks will chime in.