No insulated joiners needed. Bus may be connected, or not, at ends.
Think of your track loop as a clock. It is a continuous circle. The bus is also a continuous circle around the perimeter of the clock. Power supply sits in the middle. Legs from power supply go out in a star pattern and connect to the perimeter bus at the 12, 2, 4, 6, 8 ,10 o'clock positions. It doesn't matter if the perimeter bus is connected to itself at the 12 o'clock position.