Seems OK on my iPhone here. At least so far…

Again – do you have any tinymce plugin added to your site?

I will check I think I might

I do have TinyMCE Advanced. 

Can you do a quick test with it deactivated?

That doesn’t seem to be the issue. Unless something is cached. I will check it again in a bit 

What browser do you use? If Firefox or Chrome then you will have a mobile emulation mode you can try. Put in mobile emulation mode, run a forum page as a test and see if the editor works ok. If it doesn’t, take a look st the browser console to see if any script errors are reported…

The editor works in emulation mode. But emulation mode of your software just renders the page in a skinnier layout. It doesn’t actually provide your mobile layout for example

Emulation mode does work…  you have to emulate a specific browser (string) and the right widths…

also, do you have phone and tablet mode set up?  forum – themes – mobile phone theme (and same for tablet)…  are they set to a responsive sp theme (ie barebones, unified or reboot)?