remember - if someone on a major mobile network is uploading child photography, that device is radioactive and an instance admin is going to have options they may not have in other situations.
The idea is give instance admins control over who uploads content. Perhaps they don’t want mobile users to upload content, or perhaps they do but only major carriers, by their own definition of major.
Somewhere between “everyone” and “nobody” is an answer.
giving the instance administrator tools to help quarantine bad actors only helps, which will require layers. Reverse DNS is a cost, however; perhaps the tax is worth it when hosting images, where there is already a pause point in the end user experience, and the ramifications so severe.
Larger instances may dilligaf but a smaller instance may need to be very careful…