Dashboard Comment Previews Too short

In an up to date stand-alone WordPress installation (I have several) – I check the latest comments in the dashboard and the abbreviated comments shown are useless as the preview is too short. Despite my best efforts I cannot find where this can be changed – either in source code or via settings. At one point there was a function in functions.php but that seems to have disappeared.

Can anyone point me in the right direction, I’d like to be able to either lengthen the previews or show the whole comment in the dashboard. Any help would be much appreciated.