You mean the notifications in the message window? As far as I know, that's all coded inside the message style. Someone with more knowledge about message styles might be able to help you remove them...
I was more interested in the contact notifications in the message window.
The ones in bright red color (minimal style) that keeps flooding my chats when people idle, comes back, idles, comes back, idles.. you get the picture.
I've been sniffing around in the message-style-file, and if I sniff some more, maybe I'm able to mod it.
to edit the status messages out of the built in Minimal message theme:
be sure to quit Adium before you do this.
1. Show Package Contents on Adium.app
2. go to Contents/Resources/Message Styles
3. Show Package Contents on Minimal.AdiumMessageStyle
4. go to Contents/Resources
5. open Status.html in you preferred editor and delete all the code
6. save the edited Status.html
7. relaunch Adium and enjoy your total lack of status messages.