Yes, with a control vector per user-persona pair. In the blog, they start with a fixed number of personas (happy, sad, baseline) and then use PCA to figure out

Yes, with a control vector per user-persona pair. In the blog, they start with a fixed number of personas (happy, sad, baseline) and then use PCA to figure out the control vectors for each persona. You could easily do this for each distinct user-persona (provided you can come up with the data).