Constant hierarchical pins are generally not a problem, but they are still worth investigating. When RC propagates constants across hierarchical boundaries, it will tie the pin to 1'b0. The other side of that hierarchical pin will have nothing attached to it. It effectively becomes an unused hierarchical pin, but RC, by default, will tie it off so it is not undriven.
What you need to do, to further investigate, is run "check_design -constant" and look at any constant hierarchical pins have a fanout greater than 0. A fanout of 0 means that it is an unused hier pin, which is not an issue. For example:
design 'dtmf_chip' has the following constant input hierarchical pin(s)/designs/dtmf_chip/instances_hier/JTAG_MODULE/pins_in/JTAG_SE (fanout : 5)/designs/dtmf_chip/instances_hier/JTAG_MODULE/pins_in/JTAG_TEST_ENABLE (fanout : 4)/designs/dtmf_chip/instances_hier/JTAG_MODULE/pins_in/JTAG_IOTEST (fanout : 1)/designs/dtmf_chip/instances_hier/JTAG_MODULE/pins_in/JTAG_TEST_CLOCK (fanout : 1)/designs/dtmf_chip/instances_hier/JTAG_MODULE/pins_in/JTAG_INSTR_CAPTURE_2 (fanout : 1)/designs/dtmf_chip/instances_hier/JTAG_MODULE/pins_in/JTAG_POR (fanout : 1)/designs/dtmf_chip/instances_hier/DTMF_INST3/pins_in/tdsp_pso (fanout : 0)/designs/dtmf_chip/instances_hier/DTMF_INST3/pins_in/int (fanout : 0)/designs/dtmf_chip/instances_hier/DTMF_INST2/pins_in/tdsp_pso (fanout : 0)/designs/dtmf_chip/instances_hier/DTMF_INST2/pins_in/int (fanout : 0)/designs/dtmf_chip/instances_hier/DTMF_INST1/pins_in/tdsp_pso (fanout : 0)
In this case, some of the JTAG_MODULE pins are tied off, which I expect, and all the rest of a fanout of 0. No problems here.