While the developer's decision must be respected, I don't really understand it. Why not simply ban the troll instead of engaging with them in any way? I wouldn't want to give a troll any power or influence at all.
It's still effort. If you have someone shitting up your PRs with personal complaints you can either put the effort in to squelch the opponent or you can just walk away. For unpaid FOSS work there is often very little to be gained except for a bit of self satisfaction and kudos from the community.
It's easy to walk away from an ungrateful community if you don't have gold in your pockets to soften the blows.
Alternatively, people can instead choose to NOT be dicks to people who are altruistically developing stuff for no compensation and the net benefit of our industry.
It's easy to walk away from an ungrateful community if you don't have gold in your pockets to soften the blows.