You just dropped a mind bomb on me. Suddenly things make sense :o

Sorry, are you converting it, lossily, twice? That’s like twice the lossiness! Just convert it once.

I believe it just means you need to retrieve the post via your logged-in instance. Basically make sure the URL begins with your instance. This is one of my frustrations. You click on a lemmy link but can’t interact with the post unless you are logged in. So you have to go to your own instance and manually search for the post?