I read @Laurent.O's question differently, I think, than what you asked there.
I thought of the "Announcements" category as being similar to the (former, I think) firstname.lastname@example.org mailing list, which was described as:
A low-volume, moderated list for announcements, only. (These are posted on the
users list too, no need to subscribe to both.)
Here are all of the posts that were made to that list in the year 2017:
Those sorts of things are in the "Announcements" category, but it's also been getting posts like conference calls for papers that were formerly sent only to the
racket-users list. Those things certainly fit within the normal meaning of the word "announcements", but I think there's value in marking some narrower category of announcements—maybe something more like "announcements from Racket" than "things you want to announce to Racketeers." I don't think it needs to be quite as low-volume as the old
announce list, necessarily.
Rather than making "Announcements" silent by default, I'd suggest keeping it to things that are justified in being noisy by default. (I'd be equally happy with leaving "Announcements" in its current role, but without the default notifications, and calling the low-volume-with-default-notifications category something else.)
For example, I use mailing-list mode just as I was (am) subscribed to the users list, and I wouldn't want to get emails for everything except announcements. But "Announcements" is even more "noisy" than that: posts show up as notifications in the web UI.
I think that's a reasonable default for release announcements and a little bit more, but probably for a narrower category than the current "Announcements".
(Though obviously it hasn't bothered me enough to change my settings.)
P.S. I don't know where the source of https://lists.racket-lang.org is, but it looks like it's in need of some updates, e.g. re the end of the