The reason: Twitter just went downhill even further due to the AI training thing that just happened. Plus, anyone that you blocked can and WILL see your posts even though they can't interact with them (which makes blocking completely useless). It's why I had to nuke all my Twitter accounts at this point.
Also, for all Bluesky newbs: here's a guide that RunicIllusionist made (including lists of users to mass-block and avoid.
RunicIllusionist made (including lists of users to mass-block and avoid.
