If you mean a static salt, that could help mitigate against hacks (if the attacker has access to the database but not the code), but where adtech is concerned it's probably more realistic to assume that the datasets they're using were disclosed willingly. If you mean using a different salt for each address, that could work for some use cases, but it wouldn't work for the use case described in the blog post, since Touch Surgery needs to be able to lookup whether a given address is in the database (to see whether they've previously declined an invitation).

Article 79 says that each data subject that considers that their rights under GDPR have been violated by a controller or processor has the right to an effective judicial remedy, which may be brought before a court in either the Member State where the data subject resides, or where the controller or processor has an establishment.

This is distinct from administrative and non-judicial remedies.

That sure sounds like suing.