This initially confused me. I assumed the dictionary of obscure sorrows was a list of existing words for obscure sorrows, but I know watashi ato means “I” “after” literally in Japanese so it didn’t sound like a real word. The words in the blog are actually invented to describe obscure sorrows.
YouTube allows you to see the view drop-off at every second, so the creator of the video can see people skipping the sponsor section.
I’m guessing that sponsors probably look at click through or view count. I believe sponsors that care about views will ask to see this chart in the future if they don’t ask for it now.