“-” and “_” additionally seem to fall under a rare case of wrong case-insensitivity. I tried to select all hosts with a “-” which were accidently created. And I deleted all hosts, because all hosts with “_” weren’t filtered out.
There is no “~” in front of the filter pattern and “-” and “_” shouldn’t be misunderstood as regexp.
I checked in one of my systems.
A single letter irrelevant if letter/number or anything else is not working and shows every time all host objects.
But “-S” or “_S” shows in my system the correct hosts.
In my 2.1.0p5.cre the filter you mention in Setup > Hosts never has worked at all, whether I do partial or full host name, it just keep showing all hosts. So I stopped trying …
The Display > Search hosts does work, which I use instead.