How do you comment on a Tumblr post?

[Matt]

I just got a Tumblr account. How do you comment on a post? I see others do it but I don't see anything like a reply button. I tried clicking reblog and editing the post to add my own comment, but when I went back to the original post my comment was not there. I even tried Google searching and all I found is that there used to be a reply button, but now it's gone?

[Laurie]

I'm pretty sure your comment will only show when you reblog it, and it will only be on your reblog of the post and whoever reblogs your reblog.