Forum italic font doesn't work on iPhone

I’ve noticed for a while now that italics don’t work on the forum any more on my phone. The option is there, but it doesn’t actually display italic text.

Using Firefox for iPhone. It works in Firefox for Windows.

Quick test to see if this works now…

Looks like this is not working on safari in general, not only on iPhones.

I see the italics on the mail notification in the iPhone mail app, but not in the Firefox app where I use the forum.

Problem is that on iOS third-party browser need to use the safari rendering engine (webkit), as apple does not allow any different engines. So that makes sense, that you see the issue on Firefox as well.
I think I know where the problem comes from and will take a look.