It doesn't necessarily mean they have puritanical standards. But for me it would offer a glimpse into what its like to be a developer at a company. Like, does the company tell developers to just "make it work" in the quickest amount of time possible or does it let them come up with a proper, maintainable solution thats not going to cause headaches for future developers?

If I see a codebase that is blatantly vulnerable to something like SQL injection (i.e. GET parameters being referenced directly in SQL query strings) then this would probably be a deal breaker for me. I get that nothings perfect but something like that would indicate an extremely poor competency of the development team.

EDIT: That said there is another side of the coin - the kind of place where developers spend hours discussing things like how to name a class or a variable. That would also be a frustrating place to work in - its about getting the balance right. Also seeing the way the developers talk about their code would be interesting - are they dead-set and have an "emotional" attachment to their way of doing things - or are they open to new ideas and willing to discuss pros/cons of differing solutions and make compromises as a team.