The game runs fine, only, when I enable display com positing and turn on transparency vendetta becomes transparent in full screen mode. It's a hassle switching it on and off all the time.

X11 doesn't really have a "full screen mode" concept. What games like us do for "full screen" is simply adjust the desktop to the window size. So, yes, it will still be treated in many respects (such as transparency) as a normal window by the window manager.

I don't know if we even could work around this, and considering it's something that only impacts specific cases on one distro, it's not likely to be a peak priority for us.

At least in virtualbox the game works fine with slack 13.1 + xfce. Could be that compoiting is just more forgiving in vbox though..

Do you by any chance have some odd window manager settings or an old xfce version?

I'm assuming you're using Compiz for compositing? If so, you can go into the transparency settings and add a rule for it to ignore Vendetta's window.
Another option is to find the program "compiz-switch" and install it. It gives you a little button to turn compiz on and off.

He specifically said he is using xfce, Ozymandias. Reading is helpful.

You know, this is weird, but it works correctly now.

I think this is what I may have done:

1 - Enable display compositing
2 - Start Vendetta Online
3 - Enable window mode
4 - Enable full screen mode
5 - Exit the game
6 - Logoff and startx

OR, you can probably just enable display compositing, logoff, and startx. Something I probably should have done anyway.

I know it's not a big concern and I didn't expect it to be because I can just turn compositing off when I play... hopefully this helps other people who encounter the same problem though.

Thanks!