In a large mixing bowl, combine jerk seasoning, olive oil, freshly squeezed lime juice, minced garlic, and salt. Whisk until well blended, then add the chicken thighs, coating them thoroughly with the marinade. Cover and refrigerate for at least 1 hour, preferably overnight for maximum flavor.

In another bowl, mix diced pineapple, chopped red bell pepper, finely chopped red onion, and minced jalapeño if desired. Drizzle with lime juice and a pinch of salt, mixing gently. Let sit for 15-20 minutes to meld flavors.

Preheat the grill to medium-high heat (375°F to 400°F). Remove marinated chicken from the fridge, letting excess marinade drip off. Grill chicken skin-side down for 7-9 minutes per side, until the skin is crispy and the internal temperature reaches 165°F.

Transfer grilled chicken to a plate and let rest for 5 minutes. This allows juices to redistribute. Slice the chicken and top with pineapple salsa. Serve immediately.