I leave the keyboard frequently, and anything like making a parchment and laying down at the characters feet would be more trouble than its worth.
If someone was emoting near the character when i come back, I always apologize to the player with a quick tell. Its not a big deal, its a consequence of playing while there is possibility of interruption. For me there is about only 4 hours a day that I can do /anything/ without distraction. So, when I come across AFK, I usually just AFK with them and be patient.
Not worth the trouble? Come on...
It's easy to @write title on a parchment and then always have it there to use. It may take less time opening inventory, find parchment, right click on it, drop. And that way you don't have to apologize to those who wasted their time trying to RP with you. They wouldn't have wasted their time trying to do that if they saw the parchment either.
Sorry, I just do a big sigh when I do two long emotes and get nothing in return, realizing a person is AFK. Of course there are situations I find myself compelled to wait, like for a character I RP with on regular basis, and that my character knows fairly well. But as for the others, such a thing just kills my willingness to stay....fast. I'm so out of there.