For what it's worth, using the WebAIM Contrast Checker to compare
#31aa9a (the unread question text title color) and the white background returns a contrast ratio of 2.86:1. This narrowly fails WCAG 2.0 level AA guidelines for headlines.
That said, darkening it to meet the standard of 3:1 doesn't change the color all that much:
Moreover, this contrast ratio is comparable to that of various other sites; in fact, Bicycles is the site where I personally find the text most faded. I think the difference here is that the hyperlink color is so similar to the background color and image, and thus may wash out a bit.
Increasing the stroke width makes the text stand out more, but a standard bold weight of 700 is on the dramatic side— this may be why so few Stacks use bold for question titles, e.g. GameDev and Photography. It introduces an incongruity between the fatter letterforms of the headlines and the lower x-heights of the font reflected in the logo.
As I noted in a comment, one might argue for using a different typeface with thicker strokes, though this would be a non-trivial change to the design. Here are a couple more samples using Roboto and Georgia, against the same image as above: