I'd say it's mostly not serious, in the same [kayfabe](https://en.wikipedia.org/wiki/Kayfabe) tone as "professional wrestling" where it's known to those that are in the know that it's all a show.
The website linked in this post (invisibleoranges) is a reference to a hand gesture a lot of metal artists and audiences make when performing/listening that appears to look as though they're holding invisible oranges, tongue firmly in cheek.
The website linked in this post (invisibleoranges) is a reference to a hand gesture a lot of metal artists and audiences make when performing/listening that appears to look as though they're holding invisible oranges, tongue firmly in cheek.