Interesting point. I would imagine that it's this way round because traditionally, default HTML visited links were darker than non-visited links, and I'd guess that since our site has the generic stack exchange beta style and the design brief would have been something general and generic, they went with a design that used default patterns.
Your reasoning is good and I agree, it doesn't make sense in the context of headings that are wholly links. It does make sense in the context of links within dark or black body text, as the 'visited' colour becomes closer to the other text and therefore stands out less compared to the lighter non-visited links, but I agree it makes little sense in this context.
Huh. Guess what. They actually reversed that pattern within body text (see the two example links I dropped in the paragraph above). So in body text, it's the opposite of the default pattern, meaning that again, it's the visited links that stand out most strongly.
Well, that discounts my theory... I can see only three other possible explanations:
- Giving benefit of the doubt: They have a reason we can't think of why they expect people to be more interested in links to places they've already been. Maybe some hangover from before the notifications system was introduced?
- The conspiracy theory: It's an extra incentive for beta sites like ours to get more users and get out of beta, so we can get rid of the counter-intuitive link highlighting...
- Circumstances: Something involving working late, a stubborn client or stakeholder, and/or some other malign influence