I was reading a question on aviation.stackexchange that had a number of comments. When I clicked on add/show comments to read the rest a small help window came up on the miniformatting in the comment field. Most were things I know, but there was a Learn More button that took me to a longer page that could be very helpful. This should be added to math (and the other sites on the network). Does the linebreak option there work here? It has been requested.
The comment help is shown automatically to users under 100 reputation points. This is SE network-wide. You saw it on Aviation because of that one downvote that dropped your reputation below the threshold.
Newlines in comments have been requested many times and declined as many times.