Nope, it’s an absolute nightmare. The post basically outlines how you could feasibly exploit data across a majority of the Lemmy network without much effort at all.
With a bit more effort you could also link the Lemmy accounts to the users email, as becoming an admin is as simple as hosting your own instance and getting users to join.
Boom you have a business case of profiling people on Lemmy and selling those profiles to advertisers, stalkers and perverts alike.