Swipe and text selection are mutually-exclusive. The tap detection of the swipe library interrupts any text selection. The easier way to have text selection is to turn off the swipe feature.
If you want to maintain the swipe and override this behavior, you could try modifying the following code in assets/js/in5.config.js:
excludedElements:$.fn.swipe.defaults.excludedElements+", .mejs-overlay-button, map",
So that it includes an exclusion for the <p> tag:
excludedElements:$.fn.swipe.defaults.excludedElements+", .mejs-overlay-button, map, p",
This should allow text selection, but it greatly reduces the area of your pages where a swipe will be detected.
This can now be done by attaching a CSS file using the Resources section of the in5 (which won't have to be re-edited). The CSS file should contain the following code to ignore the swipe gestures over paragraphs of text.