On a grill / BBQ, definitely not necessary.
If you are frying / pan searing / roasting, AND you want them to get crispy, then I would definitely recommend that.
Discussion
(It’s not about the bitterness IMO)
So it’s more about moisture for you?
I don’t cook them often, I mostly do this recipe from an old book « caponata » I feel it’s sweeter if salted and drained.
100% if you salt them and let them sit for a couple hours, it’s amazing how much water they lose. Getting rid of the water is key for crispness if frying etc