With a text asking users only to agree when they (now) really see a reason for this specific ID. (As opposed to just bowing before the supposedly superior knowledge of the identyfier.) Admittedly finding a nice but clear way to word this may be hard.
Background: I’ve only recently started to do more first IDs or corrections myself. I rarely am 100% sure, but I think it should be fine to give IDs if I am 95% sure. I’ll probably be corrected 1 in out of 20 times and learn from that a lot. However, like anyone else I see many users just agreeing immediately to my ID on their observation. In some cases these users will now have looked up the species and become convinced the ID is really correct. But I very much suspect (and I’m not the first one) that many people use the agreement as a way of saying ‘thanks’. Only that I am not half as delighted about that as they might think. :-( Instead of feeling valued I feel a learning opportunity is being taken from me.
Maybe actively discouraging people from using the agree button this way would at least reduce the problem.