I've had this add-on for several years, and I considered it useful until it came to light that in the past couple of years it's been marking certain people as anti-trans for supporting nonbinary, intersex, and transmasculine people. I don't know what happened here, but this means that a tool that was once meant to help a vulnerable set of people has now turned into some sort of guessing game as to how reliable it is and is one of the sources for a lot of infighting within the online trans community right now. Not to mention some non-white users have discussed how they've been labeled as transphobic for not fitting the typical standards of white trans people, essentially painting even bigger targets on their backs than they had before.

I rated this two stars instead of one because I've only encountered this issue on Tumblr whereas everywhere else (especially Twitter) it's been accurate. The only reason I still have it is to try and correct some of the falsely flagged ones I see, which is getting agonizingly more difficult due to this extension's definition of who counts as trans friendly becoming more narrow as time goes on.

EDIT: Seeing all the empty accounts here trying to claim this extension still works as intended and that the various transmasculine, nonbinary, intersex, and neopronoun users speaking up about its flaws are wrong has made me bump this down to one star. What a shame for what used to be such a useful add-on.
EDIT 2: If this extension is working as intended (labeling certain users/sites as transphobic), then please enlighten me as to why I've run into multiple wikis about nonbinary and other queer identities labeled as anti-trans. Not one, multiple. None of them are able to be corrected either. I am sorely disappointed.