OpenPGP user IDs as defined in OpenPGP 4880, OpenPGP, 5.11. User ID Packet (Tag 13) are formed by arbitrary strings, "Real Name (Comment) " is not more than a convention. Following the specifications, it even may be the empty string.
5.11. User ID Packet (Tag 13)
A User ID packet consists of UTF-8 text that is intended to represent
the name and email address of the key holder. By convention, it
includes an RFC 2822 [RFC2822] mail name-addr, but there are no
restrictions on its content. The packet length in the header
specifies the length of the User ID.
GnuPG (at least in version 2.1, which I used to verify this statement) does not enforce a name, either -- just omit any content. In fact, GnuPG actually seems to support empty-string user IDs!
Email address: firstname.lastname@example.org
You selected this USER-ID:
Change (N)ame, (C)omment, (E)mail or (O)kay/(Q)uit?
Not all versions of GnuPG allow free-form user IDs by default and require
Disable all checks on the form of the user ID while generating a new one. This option should only be used in very special environments as it does not ensure the de-facto
standard format of user IDs.