Perhaps related to Dynamic “add / show N more comment(s)” cannot be clicked when not logged in, this question is different in that I can click the comment link on my desktop when not logged in, but not on my iPhone. (iOS 6.1.3, built-in Safari browser).
As can be seen here, the text "show 9 more comments" is in the link colour, signifying that this can be clicked just as the name of the user who posted the last question is - but while his name can be 'clicked' leading to his profile as expected, the text "show 9 more comments" is not active:
This is the question I've used as an example.
I can see this both on an iPhone and on a Windows phone, but not on an iPad.
I haven't tried to reproduce while being logged in on either of the phones.