It sems that now (last version or so, and I don't think anything changed on my system), edge lines completely disappear in sharp concave corners. Edge lines have always been thinner there, but now they are fully hidden.
Note that I don't use the open GL rendering (lines are perfectly visible there) as I don't like it (surfaces are much too shiny, don't show subtle facet angle change, and lines that should be hidden are visible there!)
Note that I don't use the open GL rendering (lines are perfectly visible there) as I don't like it (surfaces are much too shiny, don't show subtle facet angle change, and lines that should be hidden are visible there!)