Actually, the season characters are separate from the normal characters in Diablo 4. But with a trick you could overturn the separation and now catches the resentment of the developers bon Blizzard.
What was that trick? If you want to experience all of the new Diablo 4 Season 1 content, you need a seasonal character on the Season realm. Normal characters belong to the Eternal Realm.
After the season, season characters are transferred to the Eternal Realm, before that the items and inventories should actually be strictly separated from each other.
A trick could bypass the realm separation. Pull the internet plug at the right time and you could use currency, resources and equipment from the Eternal Realm on the Season Realm. Whoever used the exploit now has to fear a ban.
You can watch the Diablo 4 Season 1 trailer here:
Diablo 4: The official announcement trailer for Season 1
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In the meantime, many reports can be found from players who either know someone who was banned because of it or who no longer have access to their account themselves.
The Community Director of Diablo 4 also reports in the Blizzard forum (via bluetracker.com): “We have also taken action against selected accounts in connection with this incident.”
On the Reddit discussion platform, the friends about the announcement are great. One thread garnered over 3,000 upvotes with more than 1,600 comments in two days (via reddit.com). A player reports here that “a buddy” was banned due to the exploit.
Is the exploit still in the game? According to the community director, the season exploit shouldn’t have been in the game for a few days. However, once the character has been dragged over, it is part of the season.
Apparently, not all players are banned, but only “selected accounts” that may have used the exploit to the fullest. It is currently unclear whether banned players have a chance of returning.
More about Season 1 of Diablo 4 can be found here: The strongest item of Season 1 is also the most annoying – What makes “Barber” so good?