Replies are for the community not just the person you’re responding to. Otherwise there would just be DMs to OP.

UnderpantsWeevil made a good point, you don’t have to take that as them wanting to debate you. You don’t even need to block them. Just stop responding, it’s not complicated.

Then you don’t have to spend the effort being negative and we end up with communities that become a positive corner of the internet.