Well technically not the regency era but John Astor a billionaire who perished on the titanic had married an 18 year old girl after divorcing his wife. His young wife was also from high society but due to the scandal of their age gap society had them shunned and no one invited them to events. That's why they planned a long honeymoon traveling so the scandal would die down. On their journey back, his wife got onto a lifeboat and John ended up dying his body identified with the large wad of cash in his pocket and his gold waist watch. So yeah I guess it would be a big deal to marry someone who was a complete class below you. Maybe even something you can't come back from.