YES! Thank you! I’ve seriously been searching for like five decades. What was the magical search phrase? “YouTube Brazil increase latency” came back with “How YouTube radicalized Brazil” and other such stories. (Turns out the article mentions “South America” rather than “Brazil”; guess my Dota instincts kicked in.)

Anyway, you rock. :)

Thank you! It was impossible to find anything on Google since any variant of "youtube", "latency" etc showed results for problems with YouTube or actual YouTube videos talking about latency.

The trick was to use HN search: "youtube latency" and select Comments. First result was a comment on https://www.forrestthewoods.com/blog/my_favorite_paradox/ which links the story in the "Bonus!" section.