Read something about possible interference
Worth exactly what you paid for the information…… In an analog world 30 years ago there might have been some truth in the statement but not anymore. Auto ranging power supplies and surface mount technology have all but put it to bed.
DC current flows from positive to negative. Scratching my head as to how running the ground (return line) to the battery would negate noise on the positive (supply side). Filtering is done on the supply side
Interference is typically caused by a failed or failing component(s) in the charging or ignition systems.
Spark plugs and ignition components where the prime offenders back before resistor plugs and electronic ignitions became the norm. The fix for “interference” is to find the offending component and replace. Line filters and such are just band-aides