Especially for people that aren't... you know.. Americans.

Unless they mean actual public figure party members which are known and probably verified.

Then it probably means which side you'd be on if you were American.

you could probably algorithmically determine it in most cases based on any number of indicators from phrases used, to communities interacted with, which hashtages are included, which cohort retweets and likes most etc... thats not even getting into simply tagging political figures with the party they officially affiliate themselves with

And how are they choosing to balance them, per capita, or just both sides should get 50%? It seems pretty clear they are making editorial decisions here. Does that break their section 230 protections?

"Section 230 protections" have nothing to do with "editorial decisions"

Please read something. Preferably section 230, which is short. Alternatively something entirely different, as long as that keeps you occupied.

>It seems pretty clear they are making editorial decisions here. Does that break their section 230 protections?

No.

https://www.techdirt.com/2020/06/23/hello-youve-been-referre...

Likely they are tracking performance verified politician accounts based on registered party affiliation. Why republican should count equal in the evaluation metric to democrat when nunerically there are less republican voters, let alone proportions on Twitter, is another question.