The mighty one seems unable to read either
https://www.bbc.co.uk/news/technology-52843986US President Donald Trump has signed an executive order aimed at removing some of the legal protections given to social media platforms.
It gives regulators the power to pursue legal actions against firms such as Facebook and Twitter for the way they police content on their platforms.
Under Section 230 of the Communications Decency Act social networks are not generally held responsible for content posted by their users, but can engage in "good-Samaritan blocking", such as removing content that is obscene, harassing or violent.
The executive order points out that this legal immunity does not apply if a social network edits content posted by its users. The order is expected to face legal challenges.
Allowing a post/msg but posting a warning after it is not considered
editing, that description is reserved for the act of "editing" where the original material is altered or reworked in some way, that has not happened in any case I know of with social media platforms.
I think all of the privately owned platforms should ban the troll, theres nothing in the law forbidding that, no posts, no editing.