It takes 3 votes, minimum, to delete a closed question. However, the number of delete votes required scales to the number of votes on the question and all its answers.
The number of votes required can increase a lot, recently there was a question that took six votes to be deleted. As for whether three isn't enough... You have to realize that for it to happen, the question needs to have been closed for at least 48h, and three 10k users have to spend their very limited deletion votes on your question. That's a stringent requirement.
As for the lost comments... Comments are supposed to be ephemeral, the focus of this website is on questions/answers. I don't even think comments turn up in a (SE) search. If you believe that observation is of lasting value to the website, you can post a question and self-answer it.