I don’t believe there is any way to do this at present–forgive me if there is, but it would be great to add a preference so that the status of any item in the database would only change from unread to read if you’ve had it open for, say, 5 seconds or so, as many email clients now do? Be helpful to at least have this as an option…
If you want to keep an item “unread” then one possibility is to use the keyboard shortcut that toggles the Read and Unread indicators – Command-K. There is also a toggle for Flagged / Not Flagged and Locked / Not Locked. (See Data > Mark). A unread document that is selected becomes read (as you noted) and command-K turns the indicator back on and leaves it on while that document is selected and after you click away.
Try it. I believe it might get you to virtually the same place?
[size=85]The Data > Mark submenu[/size]
Thanks! Have been doing that already though–it helps, but would be nice to be able to scan through a series of documents, not having actually “read” them, but having opened them, without the state changing (though one can always change it back, as you say…)