Best feature of X — bookmark
To me, the best and the most useful feature on X is bookmark. Any other features of it feels like basic, and basic is not so well — mediocre.
I don’t find verified checkmark is any useful; I could live without it. But X Pro (originally Tweetdeck), now that’s useful too; but now it is part of the more expensive plan, can’t probably pay the monthly subscription, so let’s forget that it’s even useful.
The other useful feafure of X is list. And it is amplified by the functionality of bookmark. Without bookmark feature, there’s gonna be so many things gone without processing. Lists sort them out, but bookmark got it under control.