A recent post at Lemmy.ml pointed out that images are loaded directly by Lemmy clients, and aren't proxied through any instances.
This has some implications for targeted advertising and tracking. For example, if I ran an ad network, I could post a benign-looking comment that has a tracking pixel embedded as an image. Say I posted one on a Lemmy post about cooking: when a user scrolls near that comment, the image would get loaded and I would be given an association between an IP address and device type โ some interest. If not many people use that IP and device type tuple, I could determine that you were interested in cooking and try to serve you ads for kitchenware.
Adding the option to specify the HTTP user agent when viewing images (or better yet, randomize it between a bunch of valid ones) would be a nice option for privacy-conscious users who don't want advertisers (or websites collecting HTTP request data to sell to advertisers) to be able to build profiles on them.
If you wanted to add extra value to Sync Ultra, you could even offer image proxying as one of its features :)
Edit: According to this comment, the regular Lemmy website will load embeds for direct messages. If that's also true for Sync, it means someone could find your IP address by just sending you a message with an embed. That has some even bigger privacy implications.
Edit: Sync doesn't embed the image, but it loads it to display a thumbnail:
Ideally, yeah.
I'm not confident that instances would actually enable image proxying, though. The bandwidth for that costs money, and instances don't necessarily have a consistent revenue stream that would make it feasible to run a proxy in addition to hosting the instance itself.
With Sync Ultra being a subscription, I think it would be more viable for lj to maintain an image proxy for Ultra subscribers. And if Lemmy ever adds image proxying itself, the instance proxies could be used where available instead.