ghost/core/client/app/components/gh-selectize.js

import Ember from 'ember';
import EmberSelectizeComponent from 'ember-cli-selectize/components/ember-selectize';

export default EmberSelectizeComponent.extend({

    /**
    * Event callback that is triggered when user creates a tag
    * - modified to pass the caret position to the action
    */
    _create(input, callback) {
        var caret = this._selectize.caretPos;

        // Delete user entered text
        this._selectize.setTextboxValue('');
        // Send create action

        // allow the observers and computed properties to run first
        Ember.run.schedule('actions', this, function () {
            this.sendAction('create-item', input, caret);
        });
        // We cancel the creation here, so it's up to you to include the created element
        // in the content and selection property
        callback(null);
    }

});