I'm using Firefox 22.0 on my Mac and I can confirm this defect. It's also an issue with Firefox on Windows. FWIW, I've also seen this behavior with previous versions of the browser.
And yet: I've only witnessed this defect at Ask Different. I'm a moderator at the Personal Finance & Money Stack Exchange and spend enough time there and I've never seen this happen at Money.
Consequently, I suspect the issue is related to a difference between how Ask Different has been configured/customized vs. how other Stack Exchange sites behave – or at least, vs. those SE sites that remain plain beta-themed, like Money is, currently.
For instance, on Ask Different, the following link is supposed to jump directly to the anchor for Jeremy Mullin's answer at the corresponding question:
... But it jumps to the top answer, not the one whose id is in the link. See:
(Note that if you scroll down fast enough, you'll at least see Jeremy Mullin's answer flash, like it is supposed to.)
Whereas, at Personal Finance & Money, the following link is supposed to — and does — jump directly to the anchor for fennec's answer:
@patrix had commented on this meta question: "I'll tag it as a bug but I wouldn't bet on it getting resolved." Actually, I hope the difference I've demonstrated above shows this bug has a solution in reach? e.g. Isolate & test the differences between the Ask Different theme and the plain Stack Exchange beta theme. Create a sandbox instance of Ask Different, and remove/revert-to-plain the customized JS, CSS, and other parts, one at a time, until the issue goes away, identifying the errant part. Then, determine the appropriate fix for that errant part.
Alternatively, perhaps the errant customized part can already be inferred from the debugging information presented in the other answer? Such might be obvious to the developer who did the customization work for Ask Different in the first place.