Because of how the signboard works, it's inherently not user friendly.
Players have gotten around this by using some ingenuity to simply place the sheets and notices beside the signboard. This allows the other players to read the notices from afar, without needing to walk up to the signboard, also it avoids that awful clunky conversation window that NWN uses.

Of course, while this works functionally, it
looks awfulI'm suggesting that we have a new item, (hammer & nails) that allows the users to nail things to the signboard.
The script for that item would allow the visual transform of the placed paper to line up with the signboard in a visually appealing way.
See my example below (basic script, took less than 5 minutes to toss together):
