The lemon is to neutralize the chilli residue on your fingers incase you touch your eyes or nether-regions 😜
It does taste nice when mixed with lemon too though, but it depends on what your cooking, so I wouldn't add it to the whole batch.
Also, some herbs are more versatile than others, like parsley. Basil would suit more Italian style dishes and fennel would suit well.. What ever the hell fennel suits.
Milk is the best cure for burnt mouths though, for sure!