How about you allow the non-registered users to post requests but not be able to see responses, only whether it has been answered/confirmed or how many responses there are? If they really want to know the ID of the model, they need to register. In other words, we are not really forcing you to join in the off chance someone might answer your request, but if we did answer your request, you should join if you really want to take advantage of the services this website offers.
How about you allow the non-registered users to post requests but not be able to see responses, only whether it has been answered/confirmed or how many responses there are? If they really want to know the ID of the model, they need to register. In other words, we are not really forcing you to join in the off chance someone might answer your request, but if we did answer your request, you should join if you really want to take advantage of the services this website offers.