AFK detection in halo works like this.
1) If you move more than one block you are not afk
2) If you fire a gun you are not afk.
3) If you throw a grenade you are not afk.
I will test the mouse click events again, but I tested this immensely before release and clicking the mouse always removed the afk flag.
Ignore meepafk telling you your afk it doesn't matter I'm working on a way to disable it in halo, the only afk that matters is when Halo tells you your afk.