Twice during the course of WorldCon weekend, writers came up to me and thanked me for a personalized rejection I wrote them a few years ago.
That tends to happen maybe once or twice at any given convention; it's always really nice to hear. One of the unexpected perks of being (or having been) an editor. It can be a little embarrassing, because I often don't remember the writer or their story offhand (reading a thousand subs a year will do that), so I often get a little flustered and forget to do things like ask how their writing is going. But I'm always really pleased when it happens, even if I don't do a good job of making that clear.