Section 8 Equality Act 2010 seems to define the protected characteristic as solely applying to people who in fact are married or partnered, but my impression was that one could not be lawfully discriminated against either for being married or for being unmarried. Reading the provision makes me question this. Am I missing something? What gives?
It is. Part 2 Chapter 1 Section 8 specifically says "People who are not married or civil partners do not have this characteristic."
In practical terms, a claim for unlawful dismissal would not have to rely on this Act or this Characteristic. Many company handbooks refer to avoiding discrimination on "marital status", so the claim could be made that the company had acted against policy. Not as strong as national law, but likely to succeed in absence of other factors. Single people who were expected to cover shifts that people with a family consistently avoided could argue constructive dismissal on "making unreasonable changes to working patterns or place of work without agreement" grounds. And cases of sexual harassment are as likely to refer to Sections 11 or 12 of the Act as to Section 8.
There appears to be some interest in this - north of the border if not in England and Wales - and perhaps less jurisdictionally in Bella De Paulo's article for Psychology Today, which concludes "All serious forms of prejudice and discrimination go through a similar process of going unrecognized, then getting dismissed and belittled once people start pointing them out, and in the best cases, eventually getting taken seriously. Ruth Bader Ginsburg noted that when she was first appointed to the Supreme Court, the other judges did not think gender discrimination existed. ..."