In Okular, when I set the opacity of an inline note to
0%, the note just disappears altogether, and I don't think that's the intended behavior of this setting. I've read on forums that this setting is supposed to make the background of the inline node transparent, while still retaining the border. I'm not sure what could be the cause here.
I'm running Ubuntu LTS 14.04 with kernel 3.19.0-39. The version of Okular is 0.19.3 on KDE Development Platform 4.13.3, though I'm currently using GNOME on my Ubuntu.