[protothomas]

Pressing tab will move the focus to the send button, hitting return will then send the message. Presumably this is what you did. Possibly not ideal, but I'd disagree it is an invisible, undiscoverable (tab to move focus is standard), and irrecoverable (you must also hit return).

[lignuist]

For programmers it might feel odd, if pressing tab makes the textarea loosing the focus, instead of putting a tab character in the text.

[mattstreet]

More counter-productive than odd. Since most of us are already used to using tab in browsers and forms.

But yeah, it sucks to write a real amount of text in a texbox that doesn't let you use tab. Of course you can always write in another editor and then put it in the textbox.

Even easier if you use something like this:https://addons.mozilla.org/en-us/firefox/addon/its-all-text/