I used SharpReader for the longest time. One of the features I really liked was the ability to lock a new item. Locking an item would make it normally un-deletable. It would stay locked and accessable and could only be deleted by unlocking it. It was a way of saving an item for later reference. I would like to see that in QuiteRSS.
please go to
Tools -> Options -> Feeds -> Tab Clean Up
and enable the option
Never delete starred news.
After that to lock a news just mark it with a star.
You can use a label as well. For that you need to enable the option
Never delete labeled news.