Brine the pork chops: In a large bowl, combine 4 cups lukewarm water, brown sugar, and salt and whisk until completely dissolved. Add the peppercorns, coriander seeds, thyme, garlic, and lemon slices. Add the pork chops to the bowl, making sure they are completely covered by the liquid. Set aside for 1 hour.
Set up the grill: Preheat a charcoal or gas grill to medium-high heat, and set it up with two zones: a hot side and cold (less hot) side, for direct and indirect cooking. You want the temperature to hover around 400°F.
Grill the pork chops: Remove the pork chops from the brine. Place them on a tray or plate lined with paper towels and dry completely. Season with salt and pepper and place onto the hot side of the grill. Grill for 2 to 3 minutes per side, getting some good-looking grill marks on them. Transfer the chops to the cooler side of the grill and continue to cook, rotating every minute or so, until they come to an internal temperature of 135°F, 3 to 4 minutes per side more.
Make the herb butter: Place a small grill-safe pot over the hot side of the grill. Add the butter into the pot just until melted. Remove the pot from the grill and fold in the chives, parsley, and lemon juice. Season with salt and pepper and set aside.
Serve: Once the chops are fully cooked, remove from the grill and top them with the herb butter. Let rest for about 5 minutes before serving.