It's unlikely that they meant "preferred pronoun" to be about a singular person generally, since it commonly refers to preferences about oneself.

People often use pronouns other than the ones someone prefers for a variety of reasons: sometimes the preferred pronoun is new, sometimes people forget, sometimes people don't respect that person's preferred pronoun.

Yes, quite sure. Source: Friends with people who knew them IRL.

So ... I wrote that, and it's worth mentioning that I knew Noirin before the preference for different pronouns was stated. That is, I knew Noirin, as mentioned in my blog post, during the ASF days, before they moved away from ASF activity into other areas of activism. Thus, I used the pronoun which was preferred at the time of our acquaintance. Much like people that knew me as a kid call me "Richard" and people that knew me in college call me "Rich", likewise, people that knew Noirin earlier and later will likely use different pronouns, based on the norms at the time. No disrespect is meant, just fond memories of a too-short friendship.

now they do!