Open your match's manuscript from a chat and gather a line with your finger: the page dims and that line lifts into the light for your reply. Close it now and the page comes back the way you found it — no stray mark left lying across the words.
The note about what had changed used to come round once and then be gone — close it, or simply not be looking, and there was no way back to it. Now it keeps. Open your profile and, among the app settings, there is a line called What's new; it holds those notes for you and opens them whenever you feel like reading. A random group of users has it first while we test — coming to everyone soon.