19:31
@Catija ok, couple of things here...
First of all, I think it's really important to recognize the value in allowing folks to "save face"
We tend to overlook that sometimes, particularly in the face of just how much stuff SE makes public to anyone
...but... It's a huge motivator / demotivator
For an example, look at how irritated folks get at not being able to edit posts on Twitter
EVERYONE makes stupid mistakes, and when you can't fix that - when your mistake gets quoted and passed around - it's humiliating and makes you hate the system.
We allow editing, but more than that we allow grace period edits that silently apply... Purely to serve that need to save face.
We also allow deletion, and go well out of our way to avoid rubbing your face in the stuff you've deleted... Or had deleted for you.
This is a delicate balancing act, sometimes. You don't want to confuse folks; if I think I've done something and the system implies I haven't, I get confused. I stop trusting the system... Or worse, stop trusting my own perception.
The easy solution is to just give up and make everything visible. But that falls apart really quickly for the reasons described above.
Now... This is where the relevance of self-deleted posts come into play. Given the opportunity and the awareness that they've made a grievous faux pas, most folks would just as soon delete their mistake and be done with it. And in fact, many, many people do exactly that.
The value of stuff like canned comments in review isn't really so much about letting folks know why their post is being deleted or downvoted, it's about letting them know that they've inadvertently made themselves look foolish... And a good many people take that opportunity to correct the problem before anyone else has a chance to.
But... not everyone hangs around after posting. Or understands their mistake. Or is able to admit to mistakes. Or knows how to find the "delete" link.
So it's really critical that we remove these posts before they get driven into the ground by passing voters / commenters / the OP / etc.
Not just because it makes the site look better, although long-term it does have a pretty massive effect there.
But because it gives folks a chance to move on, to save face.