This is about http://www.printculture.com. Some users can comment just fine, and some users cannot. They hit the "post comment" button and nothing happens--no error, nothing. Other users can comment just fine. The ones who cannot are using Firefox, Safari, Chrome, on Macs and PCs.
I have tried changing themes. One user suddenly became able to comment; at least two others still cannot.
I have tried deactivating plugins (all but Jetpack). No change.
Any advice or help gratefully appreciated.