TwoXChromosomes was kind of a victim of the fact that it was never in the history of Reddit made possible to change a subreddit's name without just starting over and losing all of the history (incl. top/all time sorting). When the subreddit was designed as a space for women and girls on Reddit thirteen years ago, they picked the name because of 2010 Reddit's very "science rules!" culture and wanted to evoke not just "women and girls" but "geeky women and girls that use the geek site for nerds, Reddit". They were trans-inclusionary over a decade ago, despite the name. Their current pinned post says specifically "Trans women are women. TERFs can fuck right off" in giant bold text.
I get being made uncomfortable by the name, but 2XC was trans-friendly before a lot of other more mainstream feminist spaces were.