Hi William,
If you’re talking about Quarter Notes at 120, repeated on the same string (or different strings like a scale or arpeggio) I think most harpists could do a clean pluck and flat-hand staccato. However, at Eighth Note tempo, twice that fast, it doesn’t give time for the note to be plucked and heard, then dampened. This would be much more effective written for the piano. Staccato does not bring about the best sound for a harp in general.
It of course depends on the skill of the harpist!
Hope this helps.
Cheers,
Balfour