Connecting unity7 seems to silence all of the denials, thanks! 
For the record, the following commands solves the problem:
snap connect discord:system-observe :system-observe
snap connect discord:unity7 :unity7
I’ll add this to the snapcrafters GitHub Issue…
Obviously this doesn’t help people out-of-the-box but I guess most people wouldn’t care that their logs are being flooded and the denials don’t seem to hinder the application, just need a way to silence them if the user doesn’t want to connect those interfaces but does need access to the logs (see the topic linked earlier).
The system observe interface was requested auto-connection but no votes. The unity7 interface has not been requested auto-connection, could request this if people wanted…