I don't know where you see the default as Alfaerie-SVG. What I see on this page when I open it is the Set as Abstract 1: Compound & Misc.
I suppose that what Fergus meant is that the use of this set is default in diagrams embedded in comments through use of the fen tag. The Diagram Designer itself cannot change its default set, because this would break all diagrams on the website that rely on the current default (and are using piece names that are only known in that set, or which might mean something different in the new default set).
I suppose that what Fergus meant is that the use of this set is default in diagrams embedded in comments through use of the fen tag. The Diagram Designer itself cannot change its default set, because this would break all diagrams on the website that rely on the current default (and are using piece names that are only known in that set, or which might mean something different in the new default set).