The subreddit r/celestegame tries to keep track of everyone who's gotten the Farewell golden berry; the official list only has about 20 people on them. Of course, you have to record and post your gameplay to be eligible for this list, but there can't be many more people than that who've done it.
But from the other side of things, there's actually a speedrunning category for collecting all 202 berries, including the Farewell berry. TGH just set the world record on Christmas Day, I believe, completing that chapter's golden berry on his first attempt, along with the other hard golden berries. I think this really puts into perspective how skill curves work in games; not only are there very few people who ever approach the top level of skill, but the individuals at the very top are separated by wider skill gaps than you can imagine. This is why matchmaking at the top of a ranked ladder is so hard!
I don't think I thought it would be hard, I just wasn't interested in learning precise spike tricks when I started going for golden berries. It was more interesting to see how the easy levels play out when you have to memorize and execute the whole thing at once.
ADGQ 2020 is currently going on.
That was the case for me too, until I recently picked up the game Celeste. Some of the C-sides were so evil I just gave up and never beat them (I have a wife and kids, time is limited). This is coming from someone who generally likes hard games (big fan of Dark Souls series, for example, and yes, I know "hard" is relative).
The Celeste Chapter 9 golden strawberry though... that has got to be the most evil collectible I've ever seen included in a mainstream game. I would bet <.01% of Celeste players will ever earn the Chapter 9 golden strawberry.
To put it in perspective - to earn a golden strawberry you must beat the level without dying once. If you die, you are sent all the way back to the beginning. This isn't too hard if the level only takes 10 minutes to beat like Chapter 1. However, Chapter 9 took me over 4 hours to beat and I died over 1,000 times. And not only that, if you manage to beat Chapter 9 without dying, you are transported to a secret extra level (that you've never had a chance to practice). You have one chance to beat the secret extra level without dying - only then does the game award the golden strawberry.
I can't even fathom the amount of time and practice required to accomplish this feat. It must be up there with some of those insane Mario Maker levels.