Additional feedbacks:

E tags only have 1 relay URL. The next param should be the pubkey of the e's author, like:

["e", "", "", ""]

I would use a different tag, maybe `E` for the original event. In that way, users know that the original event should not be added to the end of this collection.

`p`s are one pubkey per tag. You can't do multiple public key s in the same p-tag because relays will only index the first key.