The entire point of Twitter was that there was no such filter, it would just show the tweets of everybody you followed in a chronological order. That's why we are all pissed.
In the case of Scott Adams mentioned above, it happens to me regularly with tons of people who are absolutely unthreatening. There is certainly real censorship going on inside all these centralized platforms (like deleting content), but Occam suggests this is just Twitter trying too hard.