Hm idk, various things. If someone finds posts from months/years ago, timestamps put them in context (what "current events" are on their mind &c). Also hints if it's still fresh in mind when you reply, or if it'll be a blast from the past. (Arg for YYYYMMDD, perhaps not HHMMSS.)
replied to:Why do you need it? It’s just for stalking when someone was online and might bias to ignore older posts that could still be in —not knowing the time also makes it easier to reply whenever you feel, less pressure. I don’t have time on my desktop either, hate time :p