~~/post/ and /comment/ are also a couple other url schemes you can navigate to and fix (e.g. the https://feddit.de/post/822722 link in the OP~~. Nvm I think I just realized these numbers aren't canonical across instances. Surely the backend has an ID that every instance shares - is this exposed on the frontend? It would be cool if we could just go to lemmy.site/a9637e6c-780a-4de0-b02e-8277a54cb978 and it would navigate us to the post we want.
Also, you might want to disconnect your observer while making changes, because I think any changes you make will cause some light recursion. An example of how I did it is here.