Selling my ps3. If I don't delete the user, don't delete saved data, can someone sign into their psn account and get free trophies?
i don't believe so, the Trophies are tied to the PSN Account. if the new user was to sign out of your account and log in with theirs the trophies would sync however since it's a totally different user being logged into that profile (not to mention different console which has to be activated to the PSN Account) i dare say the old trophies would be removed first before the sync process begins (rather than doing a compare and adding new trophies and games the user have not played).
With saves they maybe able to access your save data but they can't gain any trophies from it as if you download a PS3 Save File from the net you get a message warning you it's someone else's save and you wont gain any trophies from it or any data derived from it (so you can't enter the save and re-save it as a separate save).