Where in Section 230 does it say they can add to material published by others again?No, not "arguably." You are wrong. You keep repeating the same claim, and it's not based in any fact. This is purely your own misinterpretation of Section 230.
The Escapist or Twitter or any other company can publish its own content, and they can provide a platform for others to post THEIR OWN CONTENT. They're legally liable for one, and not for the other under Section 230. And they don't "lose" 230 immunity -- which is not actually a real thing, despite what Trump or the GOP says -- because you publish your own fact checks or addendums to user-generated content. Twitter can jeopardize its immunity *in specific cases* by altering the actual Tweets of the President or others, but not for posting accompanying fact checks or alerts or anything of the like.
Honestly, this isn't hard.
Would that not constitute editing it at least editing by additon.
The fact checks are information from twitter themselves based on their fact checkers.
As I said Twitter may have strayed over the line so they're about to face being listed as a publisher in that respect.
Also again it has to be a Good Faith effort being shown which the argument is there isn't a good faith effort being undertaken by only applying the rules some of the time.