After reading a bunch of back-and-forth debate on HN about this free speech vs. private speech saga, what still confuses me is the role of corporations in this.

After reading a bunch of back-and-forth debate on HN about this free speech vs. private speech saga, what still confuses me is the role of corporations in this. Some responses say “corporations don’t legally have to protect speech” others say “corporations are people so this is 1st amendment”. What I gather is that corporations are in this nebulous legal chasm of technically-a-person while also not-a-person? So corporations can be a person at times (ex. political contributions) while not at other times (ex. limited liability)? I admit my ignorance of not knowing how corporate law works. Maybe someone can explain.