Hi Rob,
With the current gallery version, comment highlighting is fairly limited. The gallery shows the total number of comments in a gallery view (ie. like
this one), but there's no easy way to select and view new comments. You can however select a couple of comment notification options. If you go to "User control panel", then "Gallery", you'll find a couple of subscription optons which you select yourself.
The level of functionality will hopefully further improve as the gallery software developers provide new releases.