I am wondering if you're talking about the same problem, or at least a similar one, that I complained about here:
http://www.oxwall.org/forum/topic/42301
Users with Apple devices can't respond to mails. I also am using the Poly Purple theme on my site, but the problem is present with other themes too and even without plugins aside from the ones that came with the Oxwall installation. It seems like the the formatting toolbar (for bold, italic, insert link, etc.) doesn't come up. Then there is a blank space where they can't type in a response, and if you tap elsewhere on the screen it might say "undefined" instead.
I got told to use the mobile version, but that's no good for various reasons and I had it disabled on purpose.
One thing we discovered was telling Apple users to use the Chrome browser on their devices and choose the "request desktop site" option. If they do that, they can respond. It's annoying, but it's better than nothing. If I misunderstood your problem, ignore me, but it sounded similar, and maybe it will work for you too.