The strange thing for me is that I lost the ability to taste citrus (I can still taste the acidity, but not what makes it good) but gained a heightened sensitivity to other things... I can taste the preservatives in bagged salads and it sucks.

Based on https://news.ycombinator.com/item?id=27570892 seeming reasonable to me, I’m inclined to believe the less sensationalized version of the paper than the breathless headlines that ran.

Probably we are looking at the neurological effects of functional smell loss. On average, this will result in a loss of cell mass in olfactory processing regions. There is no reason to believe this is permanent or something to be alarmed about. The brain is plastic, and it changes in response to use. Not being able to smell well will result in a reduction of resources put towards smell processing. Getting and recovering from covid is depressing (loss of smell is horrible and used to induce depression in mice), and that might explain the general brain-wide trend that's the cause of the breathless headlines.

Probably the olfactory loss continues to some degree for a long time. There may be some nerve damage even if the cells that are targeted by the virus aren't nerves. These then will take a long time to heal. Smells and memories of them seem fixed, but at least in mice, appear to be a flexible entity, with successive exposure to a particular smell causing different patterns of brain activity at every new exposure (https://www.theatlantic.com/science/archive/2021/06/the-brai...) "representational drift" is the key word. This particular system is highly regenerative. It can be damaged easily, and it can recover easily. Not to say that anyone should have to get COVID19.