Which isn't many, but it might have been critical to those 4.
And given the numbers involved when we talk about YouTube, it's not like it's really as low as 4 people, it's 4 out of 1 million views on a site that generates 1 billion unique visits each month ( https://www.youtube.com/yt/press/en-GB/statistics.html ). It's actually a large number of users then.
The reach of those 1% is pretty substantial.
I have never used the feature in question, but I'd certainly think twice about removing any feature that 1% used.
Linking within the video works, but it requires that the creator of the original video does more work, and if it was not planned when the video was created then, while doable with annotations, it appears scammy.
While piggybacking may be an option for garnering initial views, using it for this purpose encourages response spam. Using good 'ol search optimization should really be the first option for content creators looking to get off the ground.
Well yeah. But you can say that for nearly any feature of program. I don't see this as a big deal.