It doesn’t font_style=3.
Annotations have changed a lot in Rhino 6 and there are a few ways to create them. Unfortunately there’s seems to be something wrong with the method you’re using and were looking into it. (RH-53086)
In the meantime this also works:
from scriptcontext import doc from Rhino.Geometry import TextEntity, Plane from Rhino.DocObjects import Font text = TextEntity.Create('xYz', Plane.WorldXY, doc.DimStyles.Current, False, 0, 0) text.Font = Font.FromQuartetProperties("Courier New", True, False) text.TextHeight = 0.1 doc.Objects.AddText(text)