I mean, you can if you want. But the finger spec doesn’t actually specify a format for the returned data, so anything can be in there. Fingies just reads data from a text file and returns that. So finger foo@server would just have fingies read the file named <data_dir>/foo and respond with whatever is in that file. It could be a real name, address, and phone number, or just a silly greeting.

In the '90s we used to put public info there, kind of like a blog. The .project and .plan files (what we were working on and what we planned to work on, work or life-related), PGP key, geek code, etc.

Some people put their work contact information (not many), but the '90s were a very different time, specially before the Eternal September, and publishing contact info like a phone or email was not too big of a deal back then (remember the white pages).

Of course, finger is now just a curiosity from the past, considering its security issues and that the most healthy way of using the internet now is not to show yourself but to hide yourself the best you can.