Looking at the source code for Stack Overflow, I noticed they have used tables and inline CSS quite a bit, also something I found odd was use of inline table attribute forma
I have no idea, but the only explanation I can come up with is that Jeff isn't as supportive of web standards as he'd like us to think and none of the team are that hot on CSS. Programmers often use cross-browser-ness, ease-of-use and numerous other supposed time benefits to excuse their lack of CSS skills. And I don't mean that as a criticism, they're probably really good at programming C#/Java/Ruby/SQL/whatever, they just can't seem to admit that they don't really know something as well us a bunch of polo-neck wearing, Mac Book wielding designers...