Spoilers below
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Nope, Hoyoel did NOT create Granfel. Granfel is an Arcanian that Hoyeol simply documented, but he didn't/couldn't document everything, because in the novel it was explicitly shown the Hoyeol didn't know everything Abt Granfel.
Also if you're reading the novel pack some tissues and be ready to cry. For some reason comedy just can't stay comedy
hiding my reply too just in case ~
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Damn okay! Thank you for telling me this, I was so disappointed by the other comment ages ago ╥﹏╥ tbh seeing you use the word document, maybe there was a translation misunderstanding happening there.
Do we know of the are others from Hoyeol's world who documented Arcanians? Or did all players do that? (Makes me think of the scene where the barbarians from Arcana recognised the red-headed barbarian player) is there then a specific reason as to why it seems like only Hoyeol and Granfel are the way they are? (Ie. Granfel's personality kind of taking over, them being connected but still separate)
Answering your questions:
As far as I know there are no other players that documented arcanians other than hoyeol.
The reason the guys at frost recognized teamin is because back when arcana was a game he spent a lot of time with the "NPC's" and built relationships with them.
Spoilers
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The reason Grandfell and Hoyeol are the way they are is because of two reasons:
1. The others assimilated with theirs avatars in game is because they are AVATARS, they have no other identity. But as I've said Grandfell isn't an avatar he's an arcanian with his own life and backstory.
2. This one is pretty big and complicated (you have to experience it on your own) so I won't say it, but them being in one body is actually Grandfell's wish. He did it to save Hoyeol.

To start things off, I have not read the novel myself. I'm simply putting a spoiler warning since my comment has to do with them.
I remember ages ago commenting here something about Hoyeol and Granfell + their worlds being connected, wondering if Grandfell is truly only Hoyeol's creation as he says, but instead they share some other cross-dimensional bond (ie. via souls) that allows their fusion to be what it is. I just remember someone replying to me ans saying nope, Hoyeol did create all of Granfell's stuff. Could someone shine some light on it?
I personally hope there is more specialty to it, as if Arcana the game was supposedly so popular, no way was Hoyeol the only cringe teen doing the 'epic and cool' OC stuff.