Blogger sometimes doesn't update comments right away, so if you leave a comment and it doesn't show up immediately, it's okay. It should appear in a few minutes.
Also there are rare circumstances where Blogger is under heavy load, and it takes longer to process. But if you add a comment and it doesn't show up within a couple hours, email me and I'll see if I can figure out what's going on. Email sent to the address at the bottom of the page will reach me (but please only use it for site-related issues, thanks ;) ).
Update: You may notice some posts don't have comments enabled. That's intentional. We're only enabling comments on the Family Discussion posts, so people can give feedback, communicate plans, etc.