I had disabled comments, but now am trying to re-enable them. In my localhost environment everything works fine, but on the live site the entire comments form doesn't show up, even though the settings under Discussion and the single.php and comment-form.php templates are identical. The source code shows that there is no form, as if the function call is being ignored.
It's not a problem with the theme, because it's the same problem with Twenty Ten. Deactivating all plugins had no effect either.
I don't know what else to look at. Any ideas? Thanks all.