From the site:
Cleave is a simple GUI application for viewing NWN chat logs colour coded by chat mode, similar to how text is displayed in the NWN chat window. Cleave also supports filtering chat lines by player name and/or chat mode. The tool can also export a filtered log back to plain text, or to HTML with all colours preserved.
Also from the site, there's this:
(http://nwstory.sourceforge.net/images/win32-01.png)
As you can see from the sidebar, you can choose to display whichever chat modes you want, squelching the others, and can select which characters' messages you want to display, as well. This is particularly useful if you were in a situation where you were RPing with one group of people and engaged in Tells or had access to the Party chat of a different group. It also can make pretty coloured HTML representations of a log, and generally can make them significantly more readable.
Edit: Also, as you can see, Layonara is so very much better in terms of RP-consistency than whatever server this was originally written for. ;)