There should be a command to list the tells you've received since login.
'tell history' would work.
tell history
Certain clients will do this for you. Zmud does for me.
Or "afk".
An afk flag in this game would be too easily abused, I believe. Just quit, and log back on when you can. I'm 99% percent sure the 15 min rule is just for switching characters. I can imagine a great deal of circumstances where afk would be abused, like in the middle of a losing pk. Or when you're sleeping in a guild hall, which every vet knows is not a safe place to go afk at, or sleeping anywhere for that matter, just pop up the afk flag to avoid pk until you're fully rested.
AFK also breaks RP immersion.
Uh... I was suggesting that the command be 'afk'.
....
....heh?
sorry for misunderstanding then, just any other mud I played that had an afk command toggled a flag that showed the persons status as afk.
Don't Imms get it though? 
Don't Imms get it though?
We also get a lounge with a cappuccino maker, and gold watches when we retire. Imm-ship rocks.
I was on an Imm-ship once... the HMS Decay I believe it was. Great fun but the bartender was dreadful.
Seriously though, tell history would be nice =D
+1