Hello there mister Black Mesa sir.
Basically, I use DVORAK, and I have a quick little shortcut to switch between DVORAK and QWERTY. No game I have ever played has had a problem with this, apart from Black Mesa.
Usually I can just switch to QWERTY and it’ll be fine. Worse case scenario is that I just have to remap the controls, but no matter what, even after remapping controls or switching to QWERTY or whatever Black Mesa will always use the default QWERTY controls and treat my keyboard like it’s in constant DVORAK so it’s completely unplayable.
The one work around for this is going all the way into my regional and language settings, and changing to QWERTY. Obviously this is a big problem, since anyone with a foreign, or otherwise different keyboard layout, is unable to play this game. Not only that, but remapping keys is totally whack anyway, and not being able to remap your keys is a terrible thing on any PC game, never mind a Source game.
Anyway, peace out.