RE: tell in duties:
I'd thought it was originally a technical limitation related to the fact that instanced content moves you to a different server and /tell <player name> <msg> could be ambiguous if there was someone in that duty with that name and someone else on your home world (possibly a friend or FC member) with the same name. But now that SE has already dealt with that problem as /tell <player name>@<world> <msg> in order to allow cross-world communication, it seems like it should have been enabled in duties as well as part of that update.