Among the few #Twitter non-features, the one that takes the cake for me is the notifications about posts published by accounts you are already following.

If I understand correctly, this is the chain of causality:

• Encourage users to follow as many accounts as possible to boost Engagment™.
  
• Timeline becomes impossible to read, filter it.
  
• Send notifications about posts that may have been missed because of the filter.

This is completely irrelevant for me since I only follow people I want to read everything they publish, and I'm doing so either on #Friendica or on Twitter where I regularly have to switch back to "Latest tweets first" from the non-chronological filtered timeline.