You can disable the auto-download. Settings > Data and storage > Media auto-download, you can choose what to auto download for mobile data/wifi/roaming.
If I host an image on Cloudflare and put the URL here, I'll know which CF datacenters are near HN users who bother clicking the link as well.
Whatsapp has this option and I'm pretty sure it is in privacy settings.
I imagine if one really wanted it to be view-once, it wouldn't go to a CDN.
Thanks for pointing this out!