Bug - Unexpected world prefix inheritance? / Feature - Inherit prefix/suffix shortcut

[Psithief]

ChatManager v1.15 (this is the latest version)
CraftBukkit 1337
PermissionsEx v1.16

PEX Backend; SQL

chat-range: 100.0
display-name-format: ''
global-message-format: (%world)%prefix%displayname%suffix &e%message
enable: true
message-format: '%prefix%displayname%suffix %message'
ranged-mode: false

Testing:
pex group GParent create
pex group GParent add modifyworld.chat
pex group GChild create
pex group GChild parents set GParent
pex group GChild parents set GParent
pex group GParent prefix "<<<"
pex group GParent prefix "{{{" city
pex group GChild prefix "---"
pex user Psithief group set GParent

(say test in world 'city')
{{{Psithief test
(as expected)

pex user Psithief group set GChild

(say test in world 'city')
---Psithief test
(wrong? I expected the same output as above.)

How can I get the more specific parent case to override the child's general case, or is this not possible?

See https://github.com/t3hk0d3/PermissionsEx/issues/113

[Psithief]

If, however, this is the intended inheritence, could I please get an inherit override shortcut somewhere in the functionality of ChatManager or PEX?