You’ll have to forgive my confusion—I learned about this feature by getting a notification out of the blue. 
I posted Give an option to stop the bulk user invite process on warning (and make that the default option) and it got mentioned twice in the (thrice-)daily summaries. Meanwhile, it’s gotten just one response from a human:
I get it. It’s the weekend and humans are only now starting to look at the forum. And I’m savvy enough to figure out how to mute the bots. But it certainly wasn’t opt-in for me.
Plus the mentions are so dull:
I mean it’s accurate, which is nice. But compare that to the way it shows up in Latest:
The only thing the summary adds is “shared a personal use case”.
I guess I’m not sure who is reading these frequent summaries and not reading the list of threads normally. If it works for those people, awesome. But maybe mute forum summaries by default?