Agreed, a notification about deletion and at least a link to the now-private archived page for a few days would be welcome. At least I got an email with my comments after I complained that I couldn’t reuse my meticulously written feature request. I’ll create a new topic from that soon.
It is definitely interesting that they mercilessly hard-delete topics even with potentially useful discussions, while we debate an occasional deletion of “obviously useless” topics. I accept a never delete policy though, as long as the search results are not cluttered with those.
And yes, being able to use Discourse for Slicer for free is a huge perk for sure.