As the title says, there is a bug in the chat, people who are offline appear online.

Yep, this needs to be fixed. When we try /who in /chat namehere, it shows that people are online when they are offline.

Do they appear as online on the friends list as well? It's possible the community platform in general is bugged as opposed to only chats.

Sounds like the same problem as the friends list where people will appear as offline but they are most definitely online. I'm guessing everything is linked to the community platform