I haven't found a way to do this (yet) so I guess this is not (yet) a feature. Maybe you add an Tag for Finish, Start etc. Textmessages to have some individual "talking" to the player that accepts the quest(s). :)

Recommended Tag:
<player> or <name> but I guess "name" is not good to seperate from NPC Name

Example:
Hey <player>, thanks for bringing me 4 nice Apples.

Thanks for your great plugin and hard work.

Cya