This buyer will not contact you if there is a problem. I shipped an item and it apparently arrived damaged but I only found out due to back feedback left.

For another seller I see that they left a slew of negative feedbacks, no doubt without contacting the seller.

They leave a lot of negative and neutral feedback. While it is possible they are having some bad experiences, their lack of contact leads me to believe they don't understand how eBay works and they leave feedback emotionally without contacting the seller.

I would block this buyer if I were you because even if you package your items very carefully, it doesn't matter, the item could arrive damaged. If this buyer receives a damaged item they will not contact you, they will leave you bad feedback and move on.