On the mobile version of PMC, you can't switch to another page of comments on a submission from either Safari or Google Chrome. I didn't check any other browser to see if it was an issue there, but I know that with those two sites, it's an issue. When you try to switch to page 2(or other pages) of a comment section on a submission, it will go to the next page, but none of the comments will appear. Page 1 displays perfectly fine.
As far as I know, this has been a problem for a couple months now, but was either never reported or never reported publicly, although I know that other people have experienced this problem too. This could also be exclusively an iOS error, as the other people experiencing the problem all reproduced the same results on varying generations of iPhones, but all running the same browsers and software.