I do not. As far as I’m aware, this is usually countered through a proper way to follow through on reports. If you host user-generated content, have an abuse contact who will instantly act on reports, delete reported content, and report whatever metadata came along with the upload to the authorities if necessary.

The bookkeeping code for keeping track of unused uploads has a cost attributed to it. I claim that most providers are not willing to pay that cost proactively, and prefer to act on reports.

I can only extrapolate from my own experience though. No idea how the industry at large really handles or reasons about this.

This is not unique to Lemmy. You can do the same on Slack, Discord, Teams, GitHub, … Finding unused resources isn’t trivial, and you’re usually better off ignoring the noise.

If you upload illegal content somewhere, and then tell the FBI about it, being the only person knowing the URL, let me know how that turns out.

Checking every single image ID against all stored text blobs is not trivial. Most platforms don’t do this. It’s cheaper to just ignore the unused images.