Some of these arguments are a little questionable imo.

"It reads well everywhere else in the SQL query:"

You can alias the table names and have it read well in all places, and this mostly only matters if you are actually writing SQL and not using an ORM directly, which the next point seems to imply you would be using.

"The name of the class you’ll store the data into is singular (User). You therefore have a mismatch, and in ORMs (e.g., Rails) they often automatically pluralize, with the predictable result of seeing tables with names like addresss."

Almost any modern "pluralize" implementation would handle this correctly. Rails would call the table `addresses`.

"Some relations are already plural. Say you have a class called UserFacts that store miscellaneous information about a user, like age and favorite color. What will you call the database table?"

You would call the table user_facts... Am I missing something?