Hi, I mostly observe and identify arachnids on iNat. There are quite a few observations of chigger mites (Trombiculidae) that are simply pictures of sores or rashes, with no evidence of any organism. There is no way to tell if the sores are due to chiggers, some other kind of biting or stinging creature, poison ivy, allergies, eczema, etc. While these images are no doubt submitted in good faith, they are not verifiable or useful for identification—for the vast majority of arthropod bites/stings, there is no way to identify the organism based on the mark they leave.
Are such observations accepted on iNaturalist? If not, how should they be identified/flagged?
They are accepted, and the proper ID for them is whatever you can made an educated resonable guess on. If it’s clearly some form of small bite, Arthropoda is a fair guess. An unknown rash could be from a plant, an allergy, a virus, etc., so the ID would be Life. Use your best judgement.
In rare cases it may be possible to diagnose further, but yes, in many cases we will be stuck with a very coarse ID.