When trying to compose a new topic post or PM, the topic bar is missing (hidden).
Because screen real estate is limited, some UI elements are intentionally left out.
Maybe if you can post a mock-up of where it could be without causing problems for any other mobile devices it could be put in?
It’s bigger than a real estate problem. Without the topic bar you can send a new PM or post a new topic. It won’t let you!
When composing a new PM or topic the bar needs to be shown. It’s hidden behind the message box. Move the box down a bit.
What iPhone / iOS versions are you using?
I can reproduce in iOS 10 (it’s fine in 11) — Likely a flexbox issue; I’m taking a look now
iPhone 6S iOS 10.3.2
Just pushed a fix, there was a line of CSS hanging around that wasn’t doing much aside from causing an iOS10 bug. It will be live on meta at some point today.