Version:            (using KDE 3.5.9)
Installed from:    Ubuntu Packages

Currently, it is possible to mark messages as action items, which just adds an icon in front of the message title in the message list. 

Additionally, it is possible to display this icon in a column of its own (right click on the message list table header). 

I suggest adding the possibility to enter a comment/annotation/description to a message marked as action item. When marking a message "action item", a dialog could pop up for entering the description. The description could be shown on mouse over or in the "action item" column if shown. 
An alternative way of entering the annotation could be directly in the action item column in the message list (in place editing, no pop up dialog required). 

Rationale: 

Marking a message "action item" is only partially useful without writing down what the required action actually is, so one doesn't have to remember it or work through the message again once one decides to tackle the action item. 

An annotation feature whould be useful especially to those who (like me) keep their inbox empty by following the highly praised GTD (Getting Things Done) workflow by David Allen (see http://en.wikipedia.org/wiki/GTD). The key concept there is to always define the next physical action on any "action item". The most efficient way to keep these "next physical action definitions" in the context of e-mail whould be to keep them with the e-mails. 

I'd really like to have the annotation displayed in a column in the message list so I can see at a glance what is to be done about the action item messages.