I get the Oops! Something Bad Happened! ASPX 500 error page whenever I try and view any user profile using the mobile web view. This happens on any of the Stack Exchange sites:
Clicking on a different link (say, the homepage), then switching back to the full site view makes it possible view profile pages, but that's not much of an option on an iPhone, of course.
To reproduce, go to a user profile, and click on the mobile view link in the footer. To get back, click on Users or Tags and then on the full site link in the footer. Or use a mobile device browser, which is served the mobile view by default.
Site revision: 2015.2.13.2296 (Meta 2015.2.13.3073)