As one of the devs of the project, I will try to answer your questions as much as possible.
Some creators have already branched out and are posting some of their content to multiple platforms (maybe with different titles/thumbnails targeted for the specific platform). That would show up in my feed multiple times and I would have to click on each to find out I've already watched it. Do you try to deal with that in any way?
You subscribe to the creator, not the platform identity.
There are also very simple dedup algorithms to try and deduplicate your feed. However, they can probably still be improved.