The change in behaviour is related to
this bug report, it's not a bug but a fix.
Quoting
versions.txt:
01/11/2007 - mIRC v6.31
(...)
8.Fixed /window -dh not hiding desktop window.
(...)
A window -[whatever]h[whatever] should never pop up when the window is created. Be it on the desctop or not - thats what I expect if I use the -h switch. It might break current scripts, that's annoying but none the less it's a legitimate correction.
As per switch -h its suppose to "hide window (window only appears in Window menu)" which to me is useless there
Window commands (think of draw- or line commands, or filter) are much faster if the window is hidden.
For example: if I use custom windows to show some info, quite often I create them as hidden windows first, next I add/sort etc the data I want to show, and only then I show up the window itself.
