And to make it worse, they started sending that tracking data through "functionality" endpoints to make it difficult or impossible for extensions like uBlock Origin to block without breaking the site. I believe it would pick a random endpoint out of a few possible choices, but as one example, it would sometimes use the same endpoint as voting, so that couldn't be blocked without also preventing you from being able to vote.

It's possible to detect the difference between the request types if you examine the actual data on them, but the common privacy extensions don't usually examine the requests on that level.

Not that I condone it, but FWIW this is a common form of analytics called session recording. I use it on back office apps for troubleshooting, but I would be horrified if someone asked me to add it to a consumer facing app that people use in their day to day lives.

That's crazy. By the way it probably even is possible to fingerptint a user by their mouse moving patterns.