[UPDATE] **Unable to replicate the bug the following day, preserving the post for the moment in case things go "pear shaped" again.**
Tested this today on my level 5 Drow Assassin, copy/pasted my bug report. Didn't find anything when I searched forums or on the known issues list.
"Midnight Greetings allows you to use INT to damage. When you take the Assassin Enhancement "Dagger in the Back" it allows you to use DEX to damage with daggers and kukris. However the enhancement is not taking the higher of the two and only lets you use DEX for damage, which is counter-intuitive to most Assassin builds since INT is (generally) the focus stat.
I have not tested this with Epic Midnight Greetings as my character is only level 5 as of this moment."
Is anyone able to confirm this or test on other races and Epic Midnight Greetings? I was really looking forward to EMG, certainly not the "best" item but with INT damage I think it is competitive.