I usually use MN on a laptop, but we were away recently and I only had my phone, so was using the app.
The app has a little funnel thing at the top which allows you to filter by OPs posts only. This funnel is visible at all times, so if you get bored scrolling through, you can just filter by OP at any time.
I'm on my laptop today and had bookmarked a thread which is quite long and fast moving. There was no way to check whether the OP had posted any further updates without going back to the top of the thread and hitting "see all", but if I had been on the app then I could have just pressed the funnel.
Is there any chance that this could be an option outside of the app?
Just as an aside, "see all" (and probably the funnel too) wouldn't have helped me in this particular case as the OP had name changed within the thread, but that's a completely different issue!