A few years ago, it was proposed that herbalist shops were made no-loc to prevent people locating and porting on potions. However, this has pk implications, since that allows people to hide in those rooms, off-loc. Instead, potions were made no-loc, but that also has pk implications.
I opted for the slightly more work way and made a mob-only no-loc for herbalists. Meaning all potions are now locatable again (after rent/unrent or boot), shops remain locatable, but the stock herbalists and hedgedoctors carry will not be locatable.