/**
 * @function
 * @this AuthenticationsPage
 * @return {Promise} a Promise that returns {@code undefined} on success and {@code Error} on
 *   failure
 */

This is a function, not a constructor, yet I am getting the Redundant JsDoc @returns error on the @return line.

You asked what kind of JsDoc I am using... I'm not actually producing any documentation from this yet. I am currently coding this (mostly) blind using http://usejsdoc.org/ as reference and https://netbeans.org/ for some light syntax validation (they have some built-in JsDoc engine but it's not clear which).