Josh - he's saying that you shouldn't solder separate sections of rail together because all that metal will expand at a different rate than the benchwork and cause kinks. Either use the joint connectors without solder, or don't use them at all. Solder feeder wires directly to each individual section of rail and not joiners. Electrical contact will be much improved with this method, and you will have left some room for expansion and contraction of the rails.
-Kevin