Yes, you are right. The SaveFormat enumeration actually starts from 1. I have fixed the related Wiki article.
The problem in your test application is related to an already logged problem of changing Border.LineStyle to/from LineStyle.None. MS Word 2000 and 2002 require that LineWidth should be 0 when Border.LineStyle is set to LineStyle.None and be greater than 0 if Border.LineStyle is set to value other than LineStyle.None. We have added a fix in the next version that will automatically readjust LineWidth to be consistent to current LineStyle setting.
Meanwhile, as a workaround, you should always keep LineWidth consistent with LineStyle when you change LineStyle or LineWidth properties. For example, use
Builder.ParagraphFormat.Borders.Item(1).LineStyle = 0
Builder.ParagraphFormat.Borders.Item(1).LineWidth = 0
to hide the left border of a paragraph.