When RadRichTextBox.DocumentInheritsDefaultStyleSettings is set to true, lists in the document are exported to HTML with Verdana font, instead of with the font applied in the UI.

Workaround: Use modification of the document default styles ("Normal") instead of setting DocumentInheritsDefaultStyleSettings  to true, e.g.:
this.radRichTextBox.Document.StyleRepository["Normal"].SpanProperties.FontFamily = new FontFamily("Segoe UI");