I clip or pull the sides of my horse's tail, as is the "norm" in dressage.
With a horse who is generally a pasture puff, pleasure horse or the owner just does not want to appropriately groom the horse for the sport they are doing, if I have been hired to braid I will generally finish off the look with an appropriate dock braid. However in dressage we don't want to braid the entire way down the tailbone, nor do we pinwheel or braid as finely as is required in the hunters. I like to keep the size of the french braid matching to the size of the braids in the mane.
I think a well pulled and clipped dock looks far more appropriate for the dressage ring as the lines are far cleaner and simpler than with a braided dock.
They say money doesn't buy happiness -- well happiness doesn't buy horses!