What does following a task even do?

What does following a task even do?

I've been playing with task following. This is what I expected it to do:
  1. Get an email on a comment
  2. Get an email on status change
  3. Get an email on a document upload
None of those happen. I might get a notification. But Zoho's notificaitons are so broken that I get 500 a day for the tiniest updates.