Say, you start a discussion with the subject "Where are you?". Somebody replies to it changing the subject line to "I am here!". When somebody replies to this post, Moodle Mobile App gives the new post the original subject, "Where are you?", not "I am here!" as the browser does - which is the expected behaviour. I am still in Moodle 3.1 and an year or two old Mobile App. I beliege the problem is still there.