Yes, and and that a much more common convention than the one I favour. They do it partly because it keeps the factors of c out of the visible equations -- but

Yes, and and that a much more common convention than the one I favour. They do it partly because it keeps the factors of c out of the visible equations -- but I like my those cs. Another reason is that people instinctively feel that the elements of the coordinate tuple all have to have the same units. But that's not necessary when you have a metric around. Indeed keeping irregular units is helpful because it prevents you from accidentally forgetting to multiply through by the metric.