I tend not to, but only because I don't post a lot.

But I'll echo some of the answers here and say that if I would delete my post it'd be because:

• it was a duplicate
• it was posted on the wrong community
• it was not the "right kind of post" for the community
• it offers nothing of value

And fears that my post will be one of those listed above keeps me from posting.

As for comments, I also tend not to delete, but might if:

• it was a duplicate
• it was posted on the wrong thread
• it was not the "right kind of comment" for the post
• it offers nothing of value (but I tend to let this be anyways)

And again, fears that my comment will be one of those listed keeps me from commenting.