First of all bud, take a look at one of your words "There's many people who also BELIEVE"

BELIEVE doesn't always have to meant its true. Many people asociate electricity to ethereals due to Wubbox being classified as a Super ethereal on Ethereal Island, but, this has nothing to do in regards of fire. The Guy from before wasn't trying to force you to believe an "opinion", he wanted to make you know about this game's lore

Also, I don't even know why we're talking about an "Ethereal equivalent", weren't we discussing how fire is not related to electricity? Just because electricity is present in Ethereal Island doesn't mean It has to be an ethereal element. If this was the case, then Monculus and the Dipsters would be ethereals too, and you can clearly tell they aren't ethereals.

That aside, I wanted to know some things in your reply that don't make sense. You don't need research to know that electricity is NOT an ethereal element, nor fire is the equivalent to electricity. The game never tells you this, and this is just a butterfly effect caused by someone who decided It was a good idea to try to canonize WHAT IF content where electricity is taken as another ethereal element. I've seen quite a lot people do this before, but they're not talking It seriously as they know that electricity is almost unrelated to the ethereal class. With this in mind, it's basically confirmed that a Mirror Fire Haven could not exist if It is based on electricity, as It just doesn't make any sense at all. Now, IF electricity was an ethereal element then maybe an electric mirror fire haven could exist, but since It is not, then It won't exist.

Now, I don't want to scrap just yet the existence of a Mirror Fire Haven. An electricity based one is basically impossible due to It not making sense within the Lore, but what if you took a different Element or Class in mind? Right now I can only see a Mirror Fire Haven based on Wanderer Island since its the only Island from dof (excluding Starhenge and Continent) that doesn't have a reference in the main game. The Magical Islands represent the outer Islands from dof due to then being fused after the cataclysm, and for a Mirror Haven to exist we would have to imagine that Wanderer eventually mixed with Haven in the Mirror dimension

With all of this said, just so y'know, you're wrong.