>the media files attached to the message simply disappeared.
It doesn't happen when I edit the message in mitra-web
If you are using a different client, I suggest sending a bug report to them.
Also, the list of supported clients can be found in README.md : https://codeberg.org/silverpill/mitra#supported-clients
>I hope the cleanup will remove unrelated files from the filestore - because searching for it manually is almost a hopeless task. There are thousands of image files that are similar to each other.
Yes, they are removed automatically.