For future reference, Medium does tell you what the problem is when you suddenly can’t see a user anymore and you try to go to their profile:

403: Forbidden
User has blocked you and you are not allowed to access the profile you were searching for.

404: page not found
User has (voluntarily or not) left the platform and the profile you were searching for no longer exists.

Writer of fiction, blogs and erotica. Frequency in that order. Popularity in reverse.

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