How can i turn off the Instant Messenger status? (Online, Offline)

You mean online status? I don't think there is an IM status indicator...

in any case; there isn't a way to turn it off in 7.1; I believe Rick mentioned there will be a way to do it in 7.2.

You could however just remove the section from the showflat.tpl/showthreaded.tpl files (or post_side.tpl in 7.2)

I think in 7.2 this can be achieved by disabling moods in feature settings (please note that this option in the cp does not exist in anything less than 7.2, which is presantly in beta)