Most likely real. In LDAP, the "uid" attribute is commonly used to store the Unix account name. The numeric Unix uid/gid are stored in the "uidNumber"/"gidNumber" attributes.

Rachel doesn't joke much in her posts.

Why wouldn't it be for real?

Given the context of the post, the uid info is likely populated from a central source. I log into one box anywhere in their infrastructure and see who has what uids, it is evidence about who is permitted to that part of the infrastructure at that time.

Sorry, for some reason, I thought the author meant UID stands for "unix account name".

It's totally my fault for misunderstanding.