[BUG] Moderation-blocked images attached to posts are silently removed (should be noisily removed)

Is there an existing issue for this?

[X] I have searched the issues (both open and closed)

Current Behavior

There is an instance misskey.design. Many US/EU instances block image attachments on misskey.design due to the server hosting some adult content which is legal in misskey's jurisdiction but possibly not in other countries. This policy is longstanding and the policy is not itself the problem.

There's a post here: https://misskey.design/notes/9wj97s1whc Posted by user: https://misskey.design/@demidoro It is not adult content. It is the words "夏だね" and an animation of a girl looking out a window.

When viewed on the official iPhone client for Mastodon, this post shows only the words 夏だね. Not only is the image missing, there is no indication that content is missing:

Expected Behavior

The expected behavior is that the post should have some visual indicator showing that an image is missing. Tapping on the missing-content indicator should cause the missing content to be loaded from its original server.

For example, this is what appears on Mastodon.social web ("expected behavior"):

Tapping the "preview not shown" links you directly to the host server.

Meanwhile this is what appears in Tusky for Android (also "expected behavior"):

Screenshot_20240806-160600

(This is not as good as Mastodon web because tapping the button sends you to a dead link, but it at least it shows you something is missing.)

According to my friend Misty, Ivory for iPhone also has the expected behavior.

Steps To Reproduce

I do not have an iPhone to test on, however, I have confirmed the issue on two devices:

My wife's iphone, when I boosted the above post the other day. She saw the post in her feed and it looked the same as the above screenshot, text only no indication of a missing image. (We tried to get a screenshot today but were unable due to a separate bug.) My wife uses mastodon.soical, I don't know her iOS version but can get it if really needed.
My friend Misty's iPhone. Misty's phone took the above screenshot. Misty is using iOS 17.6, and the client is 2024.7 downloaded today. She is using digipres.club.

The fact it reproduces on digipres says to me this is not a server-related issue and the fact Tusky does not have the same problem indicates that it is not a problem with the API per se.

Environment

See above

Anything else?

The official Mastodon client for Android has this same problem in my testing, I filed a separate bug.

mastodon / mastodon-ios