Trading unexpectedly being disabled is the most recent example of why we need to have an in-game notification window for important updates. My partner and I just completed an Arc of Endless Archive and we planned on trading parts, and only learned about this after we attempted a trade after we picked up the parts. We would have made different plans if there was any in-game notification, but there wasn't. I'm sure there are many stories like this one thanks to the lack of communication.
You even tested the tech to send global notifications during the Twitch stream for a global reveal a while back! You also have the notification window for in-game events. These are things that should be used to benefit players so that they don't learn about unexpected changes after harm has been done.
It would also be really nice if there were summaries about important changes to skills, abilities, and other functions of the game in these windows, such as the recent combat changes to Destruction staves. It's not unexpected for there to be some changes when there's an update, but it would be nice if there were notifications about significant changes like that in-game to cue someone in to go check the forums for more details, or anything like that.