For MNHQ: today I have noticed that a number of posts that I have commented on are not showing up on "I'm on" tab on the iPhone mobile app (some are, some are not). When I go into "I'm watching" tab, I can see my posts so I know that I have indeed posted correctly. As an example, I've replied to the post about the correct way to hold a fork (which sounds ridiculous out of context) - this appears in "I'm watching" but not "I'm on".
Anyone else?