I see that chat supports markdown (just like questions / answers / comments), but it also has a back-reference feature (:messagenumber). Is this documented anywhere? Even when using the GUI (the reply button), it's not entirely obvious how it works -- e.g. :messagenumber seems to include @user (besides causing the back-reference-highlighting behaviour)
In any case, it would be nice to have "formatting help" and "preview" links for all places where you can enter markdown formatting.