For anybody who doesn't know what a front end is, the job of the front end is generally to take data from the back end and present it to the user. So for the fediverse, a front end might be the web page or app. The back end is the actual instance where you made your user.

Lots of front ends do filtering, but at the explicit instruction of the user. It's better to do it on the back end if you can because it's wasteful to send data to the front end only to throw it away. But there is a place for front end filtering, just not in secret.

So in this case, a person who used tesseract as well as, say, a lemmy web page interface, would probably expect to see the same data in both places, but the tesseract front end would actually be hiding a lot of stuff.