As a full stack developer I can assure you I can easily produce the result displayed in both those panels in the image 😏
I would post to both: at least on lemmy you can use your phone to create the post and read the replies without having to deal with reddits garbage ux on phones. Then you can just copy paste what you wrote on lemmy to reddit next time you’re on desktop/laptop.
There should be an error, but it shouldn’t say whether it was the email or password that was wrong.
That’s not really true, since on reddit only the one host can see the votes, as opposed to anyone who is willing to put the effort in.
It’s also probably to make things slightly simpler from a legal perspective.