In light of the number of meta posts complaining about deleted comments or closed questions, I think it's clear that the site itself is not communicating to new users exactly what comments are for or what is on-topic. One of the reasons I think this site feels very hostile to new users is because they do not understand the policies. The moderation actions are not expected and may feel random. If new users have different expectations, perhaps expectations from other stack exchange sites or other forums, then they are going to carry those expectations to this site.
In particular, the deletion of comments is a big issue. Users are not accustomed to having their comments deleted (seemingly randomly) by other people.
As such, one key approach is to better convey to the users what comments are for in the user experience (UX). Stack Exchange has always had a "comments are temporary" policy, but they have never been an issue to this extent.
I have been thinking about this issue particularly from the UX point of view and have thought of a couple of ideas that I have added in the answers.
Changing the "add a comment" to "suggest improvements" was a good idea, and perhaps we can look at some other changes too that communicate the site policies better with new users.
It also may be a good idea to ask over at the UX SE site if they have any suggestions about conveying to users our particular comment policies.