Yikes. I don’t have an Iphone, I will look into it but honestly that sounds like it might be above my abilities. Mobile development is difficult because of the various screen sizes and browsers. The Iphone is extremely common though So I might be able to get something fixed for that. I assume you are using the safari browser, because I am pretty sure chrome works?
Some of that is because I used nested replies. I can turn that down to one level of nesting and that should help.