Public officials would be fine blocking people on their personal accounts as long as they draw a clear line between their personal and official accounts. Trump ran afoul of the law here because he didn’t do that.
Despite being downvotes, this is on the money. Had he maintained some kind of separation between himself and the office on Twitter, it’d have been fine, but he announces policy change first on Twitter, for example.
The issue is that he had no interest in using the @potus account, because his narcissism wanted the follower bump on his personal Twitter account.