Why does the hole in Jupiter persist?

I don’t know but some folks that may have some idea said in response to this question:

“what im wondering, kind of already been answered, but if anyone can elaborate, why do these impact scars appear black, and how long will they be visible?”

“Our knowledge of these things is limited to one previous observation (SL9), so there’s a lot more to learn. Based on that impact, we might expect the scar to remain visible from a few weeks to a couple of months. The coloration is related to the particular deeper atmospheric gases exposed by the collision.”

“Spectroscopic observers found that ammonia and carbon sulfide persisted in the atmosphere for at least fourteen months after the collisions, with a considerable amount of ammonia being present in the stratosphere as opposed to its normal location in the troposphere.” (in reference to Shoemaker-Levy’s impact)

There is additional discussion here, and you might consider contacting one of the more knowledgeable types and asking them.

It may simply be due to the fact that the area is so large (about the size of the earth) that it creates its own “ecosystem” and so is more difficult to disperse as the winds may detour around the disturbed spot.