Bug/Exploit with letter delivery task

Hi, there seems to be a bug with this quest granting XP that it should not. We were using party chat to talk with a new player (I think), who has been having trouble finding people, and bleeding out in the sewers etc. - so this was an accident of being in this odd type of party-constellation.

Note: the same did not happen for Polly, who was also in the party but did not get any XP. I.e., I guess this looks more like some rare fluke/bug than an exploit.