Message from player on blacklist received

Twice now I have seen a shout from a player already on my blacklist. This appears to happen when I press O to blacklist another player. I have a screenshot showing this, but as it contains many player names on the open blacklist window, I hesitate to post it here. Please let me know if it is needed.

Time: 9/13/13 1:22am PDT
Frequency: Twice so far
World name: Behemoth
Character name: Cikala Silvercloud
NPC name:
Monster name:
Class/Level:
Party or solo: solo
In-game time:
Area and coordinates: Ul'dah
Steps: 1. Blacklist a player.
2. A little bit later, press O to open blacklist.
3. As I press O, a shout from previously blacklisted player appears in the chat window.

This has been already reported by others here as well - basically there is a brief period of teime duting loading of the BL where blacklisting itself doesn't work.

Earlier today I was playing and received a tell from an RMT seller. I immediately did /blist add <r> to add them to my blacklist then continued on my way.
An hour later I receive another tell from the same RMT seller. I know it was the exact same person because when I /blist add <r> on them I got "player already on blacklist"
Mention it to the guys in my LS, then continue playing. Another 30 minutes later and again I got a tell from the exact same RMT seller.

Reported it as a cheat because I really don't know if this is a cheat, or a bug.
Unlike the first poster though I didn't press O. I was busy killing mobs when both the second and third tells came in.