They are brilliant at managing change, which is why people keep saying "it doesn't change." No, they don't do redesigns for the sake of redesigning, but (two examples off the top of my head) they added a "past" section and they added a character count for titles when you are submitting.

Their motto is "move slow and preserve things." They do change, but not stupidly and they do so with a great deal of respect for what is currently working, which is something many, many, many people in the world utterly fail at it. It is the norm to take for granted the things that are going right, then act all surprised when changes result in throwing the baby out with the bath water.

It's enormously hard to make thoughtful tweaks of the sort the happen here, that get researched and thought through over very long periods of time and go largely unnoticed by the collective subconscious of the site. It's the sort of the thing the world needs more of, but also the world needs more commentary on "Well, we did make this, that and the other tweaks, while leaving most stuff intact." because it does tend to go unnoticed and it does tend to get characterized as "never changing."