New update released, fixed the composer field in the settings area: FIX: editor on user profile · worldismine/pm-auto-responder-for-admins@891e26b · GitHub
EDIT: One last thing. You can now set a time limit for how many hours shall pass until the next autoresponse message triggers. If a user messages you a few times in a row during the set time limit, he/she will only get one auto-response. This prevents unnecessary replies by the autoresponder if a user messages you too many times.