Developer is targeting individuals with a blacklist he maintians, enabled by default. Dev can do what he wants, but I’d like my home instance to consider removing it as a front end.
YSK post: https://lemmy.world/post/49813386
Dev post about it: https://lemmy.today/post/57096701
Blacklist: https://copyparty.adrian.place/u/?doc=policy.json

It sounds like I might not have known if I was using it or not, depending on how I accessed Lemmy.
It’s extremely unlikely that you were using it without knowing. Though if you were you’d know now because reloading the page would load Lemmy-UI instead of Tesseract. They don’t look at all alike.
edit:
https://photon.lemmy.ca/ looks very similar to tesseract, if you want to see the difference.