I’ve had this happen 3 times. Two times a loved one (wife, son) found the login and posted about it, and there was a great outpouring of love in multiple threads. We posted an announcement for those two and pointed to the main thread, then after a week, took it down, packaged in a nice pdf and mailed it to the loved one. We didn’t do the badge thing, I think mostly because I didn’t think of it, but if I had, I don’t think we would have. We had a bias toward “now” in our community management style so doing a badge probably would have felt out of place, especially after a year or so.
I wish I could find the thread on one of them, it was one of the funniest and heartfelt goodbye posts by a son that I think I’ve ever read. Included the phrase “I will always picture my father in a thong on the beach…”
The third one was a personal email from someone who had been active but had stopped because they were sick. I shared it with people who knew the user, but didn’t do anything special in the forums.
Bottom line: Allowing the grief to flow is healthy. Consider if you need any long term memorial - only you and your community can decide that.