My block list has I think 7 people on it. I only block if someone makes my Lemmy experience worse any time I see something from them. Disagreement I am fine with. It's healthy to see other viewpoints, even if I don't agree. (Or if it's an issue of morality, like not viewing minorities as people, a grim reminder that people think like that. Fortunately by the time I see those, someone else has replied on the matter.) Being inflammatory and adding no value to any discussions is what gets you blocked for me. I know I have blocked several spammers, but it appears that their accounts got deleted.
I have blocked many communities though. It's mostly porn. Furry porn, not for me. Anime porn where the subjects look too young... Just don't want to see that. Porn that just isn't my taste. I would just block NSFW but there is some NSFW that isn't necessarily porn that I want to see. (Ex: frank discussions about anatomy)The stuff that isn't porn is just communities that are inflammatory echo chambers.
I browse all because I don't have many subscriptions that are active, so that is why I have so many communities blocked.