What can I do if another user posts on my observation an ID that may be wrong?
You can ask them why they IDed it that way. You can ask people who are familiar with the species you think it is to add their ID. Other than that you can wait and hope that other identifiers come along eventually and correct it.
I agree with what Vireya said, but I also go check my own ID against field guides or keys, especially if the identifier’s profile indicates they are pretty experienced in the taxon in question. More often than I care to remember, I think I know a species, but occasionally I’m just wrong and there’s a look-alike I didn’t know about.
If I think the ID is obviously wrong, I explain it do the identifier. I have had several clearly new IDers at my observations who did not check the location and without much thought IDed it as a similar species from their continent. I also like to twitch rare birds and the ID looks out of place and sometimes someone “corrects” it to a more common local species, so I explain the situation to them. This almost invariably solves it - most people are really on iNat to learn and they are happy to discuss reasons for ID. I have also learned a lot this way, when I present my reasons for the ID and the other person points me to what is wrong in them, I also got many links to resources that helped me improve my IDs this way.
Another thing you can do, and this is what I do if the person who disagrees hasn’t responded to my question, is tag a trusted IDer of that taxon. I have a wasp guy, I have a spider guy, I have plant people, I have a bird lady, there’s a group for galls that I tag sometimes. I try to keep my IDers local so they are familiar with the species I’m looking for help with.
Even if the person who disagreed with your ID never answers, you usually get an explanation of what it is or how to ID it from someone else.
Finally, the thing to do if it’s determined you are wrong is to withdraw the original ID.
Thanks to all who replied. In this instance the person courteously withdrew the unsupported ID at my request.
Let’s not forget that in some cases the most agreed identifications are not necessarily the correct ones.
If asked on the reasons behind their ID, “contrarian” or maverick identifiers should answer. Yet, queries could sometimes remain unnoticed. So, it could be worth mentioning again an user if there are no answers.