I think a continual pattern of deleting and re-uploading observations becuase they disagree with IDs of others, especially if they have been told how to opt out of Community ID, is not great and is antithetical to how iNat works. I’d say the first thing to do is tell them how to opt out of Community ID, that’s the solution for people who don’t want to trust community feedback, with the caveat being that if the Community ID doesn’t match their ID, the observation won’t be reserach grade. If they don’t want people adding IDs to their observations, they shouldn’t be posting to iNat. You can submit a ticket to iNat about it.
You’re certain this is their specific motivation?
No, anyone can block up to three accounts for whatever reason.