[Bug]: `Delete` attributed to a moderator is rejected

### Requirements - [x] Is this a bug report? For questions or discussions use https://lemmy.ml/c/lemmy_support or the [matrix chat](https://matrix.to/#/#lemmy:matrix.org). - [x] Did you check to see if this issue already exists? - [x] Is this only a single bug? Do not put multiple bugs in one issue. - [x] Do you agree to follow the rules in our [Code of Conduct](https://join-lemmy.org/docs/code_of_conduct.html)? - [x] Is this a backend issue? Use the [lemmy-ui](https://github.com/LemmyNet/lemmy-ui) repo for UI / frontend issues. ### Summary I am sending a `Delete` activity attributed to a group moderator. Lemmy rejects it with the following response: ```json {"error":"unknown","message":"URL failed verification: Domains do not match","cause":"URL failed verification: Domains do not match"} ``` ### Steps to Reproduce 1. Create a group on a Mitra server 2. Create a post from a Lemmy server 3. Post is deleted by the group admin (who is recognized by Lemmy and is displayed in its UI) 4. Lemmy returns HTTP 400, post not deleted. ### Technical Details Activity: ```json5 { "@context": [ ... ], "actor": "https://mitra.social/users/test", "audience": "https://mitra.social/users/attributedto", "cc": [], "id": "https://mitra.social/activities/delete/019ff0a6-ec95-7390-894b-f874b956f155", "object": "https://voyager.lemmy.ml/post/19899", "proof": { ... }, "to": [ "https://www.w3.org/ns/activitystreams#Public", "https://voyager.lemmy.ml/u/silverpill", "https://mitra.social/users/attributedto", "https://mitra.social/users/attributedto/followers" ], "type": "Delete" } ``` ### Version 1.0.0-nightly-2026-08-11 ### Lemmy Instance URL https://voyager.lemmy.ml/