I have a different view here.
As a seller I am happy to have customers questions displayed. On the rare occasion i get a spam question i blackball the questioner and delete the question.
As a buyer I find it useful to know if a seller responds to questions and sometimes the question responses to other peoples queries have either reassured me this is a seller i want to buy from, or warned me this is one to avoid.
Unfortunately there will always be a small minority of bad sellers who would be very happy to set their questions settings to 'invisible' and not respond to any of them - either because they've not visted the site for ages, or because they have something to hide. I feel much safer knowing there is a way to publicly see if a seller is responding to questions.