Not using the \] for any particular reason here, I discovered this by accident. Just wondering how this can happen. I'd say Latex should either display the bracket (just like \} displays a curly bracket) or display nothing at all (like anything unknown with a backslash in front of it).
Or...
Check this formula:
\sin(x) \] \cos(x)
The \] there (click formula for source) seems to cause some strange indenting for sin(x). Is this a bug in the Latex formula generator?