I’ve been using Discourse daily since April and never even knew there was a “Dismiss All” button till I saw this thread and deciding to go hunting for it. It wasn’t obvious or intuitive that it would be hidden under the “view older posts…” link. Why would I look for it there?
I had eventually turned off notifications for likes because I didn’t see any way to dismiss them en masse, so they’d pile up, and I’d have to either ignore them or click on each one to clear it, thereby wasting time. This design could be improved.
I’m the admin of my forum too. I doubt many of our users even know this feature exists. I could survey them to be sure, but I quickly asked my g/f who’s been helping me admin, and she didn’t know it was there either.
If you need more validation that people don’t know this feature exists, that should be easy to gather.
So yeah, add my vote to making this more prominent.