In iPad's Safari, when I am opening a Stack Overflow question, I am not able to select/copy text from comments.
There is no similar issues on PC version of Safari.
The possible workaround is to save the page into Pocket, and inside the Pocket Web view I can easily copy any comments text.
Alternatively it could be CSS style (in particular
:hover) -see Voting up comments no longer possible via ipad
Another article about the possible issue of
:hover processing by iPad Safari can be found at http://www.nczonline.net/blog/2012/07/05/ios-has-a-hover-problem/.