I am the lead developer of the mobile theme, Graphene Mobile Neo. We have decided to bundle the free version of your mobile theme switching plugin with the theme due to its robustness and stability. Some of the users of our theme have also purchase the pro version of AMTS for W3TC compatibility.
Now to the question, some of our users have reported an issue where some HTML codes is appearing in contact form message area when the page is viewed on mobile devices (screenshot: http://imgur.com/MVhROoe ). After further investigation, we have determined the cause to be the “clickable phone number” feature in AMTS.
I noticed that you’re using PHP’s DOMDocument class to search for the mobile_tel class. However, when using $doc->saveXML(), sometimes additional document declaration ( <?xml … ) is added into the document, causing the layout to break and codes appearing where they shouldn’t.
A temporary fix that we’ve provided to our users is to disable this feature by commenting line 76 of any-mobile-theme-switcher-pro.php file: