The reason for the commas at the beginning, is that it is easier to add a new line at the end. That is, if you forbid a "last comma". Traditional languages don't let you do

    Html.program {
        view = view,
        update = update,
        subscriptions = \_ -> Sub.none,
        init = ( model, Cmd.none ),
    }

Because the parse would expect something to come after that last comma. And thus you would have the last line being special and different.

Also, it is much easier to look at this

    Html.program
        { view = view
        , update = update
        , subscriptions = \_ -> Sub.none
        , init = ( model, Cmd.none )
        }

And see if all of the commas are actually present ;)