VSS is shorted to other signals, sometimes on purpose, but other signal name always seems to "win". Why is this?
In the absence of LVS POWER NAME and/or LVS GROUND NAME, the "alphabetically lowest" name is chosen.
This can be controlled by listing the names of the power and ground nets using the LVS POWER NAME and LVS GROUND NAME statements in the SVRF rulefile.
LVS POWER NAME VCC VDD
LVS GROUND NAME VSS
Note: for purposes of choosing net names in the presence of text conflicts, this works for DRC as well as LVS.