Well, why not put it as a status thing, where people who care and follow can see it, or people who click on your profile, instead of having a bunch of "I'll be gone for awhile" posts? I remember when a ton of people were doing that a long time ago, I thought it was a rule that only important guys can make these posts cause of that.
The rule was actually for people to stop making "I'm leaving" threads due to how many had been posted and the tendency for them to be not-so-permanent. "I'm back" threads aren't really against the rules, though I do agree with keeping them down to profile statuses just to prevent an overwhelming amount of these threads as time passes and more people return.
