I've had Tapatalk on iPhones, iPads, Galaxy S3 and the ASUS Transformer. There has never been a chat option I've ever seen. Notifications can be setup for new posts or pm's, but you cannot see visitor messages, unless you go to the browser.

I usually toggle between Chrome and Tapatalk, depending on what I'm doing.

I've never figured out how to chat on ios or android for PC.