SitePoint forum titles are a bit of an exception. vinpkl, and many other members, have titles but do not belong to any primary group.
They are essentially custom titles that were assigned when SitePoint migrated from vBulletin to Discourse. Such members have the option of keeping their vBulletin title, having none, or using a Discourse Group or Badge title if available.
Unless I’m missing something, there is no pure CSS way to target non-Badge titles.