StackOverflow and Github repos are a wealth of information about a possible applicant. There's the code... yes. But there's also the comments on Stack Overflow and issues on Github.

Given that the person is presenting StackOverflow as an example of their profession, comments on SO would be very telling for how the person would be responding to critiques of their code and their responsiveness to questions. Much can be seen in the attitude and professionalism that would be seen in email. Things like:

* Do they write in complete sentences?

* Do they use spelling and grammar that would be appropriate to send to a client? A director?

* Do they range against all that is wrong with the world over little things?

Likewise, with Github there are issues that they have logged on other projects - do these issues contain sufficient information about the problem so that the person working on the issue can diagnose it? For issues on their own projects or projects they contribute to (and have taken ownership of the issue), are they responsive and provide useful information to help someone provide a good bug report?

I'm not too concerned with the code. That's easy to fix. But a person's attitude and providing these sites as an example of their professional mindset is something that can be difficult to get at in an interview when they are only trying to put their best on display.