ligature bracket affected by other voices

[Nancho Alvarez]

> I'm not top posting.

The ligature bracket right-end is affected by other voices.
In this example, the first ligature is printed correctly, but not the second
because there is other voice doing quarters.
---------------------------------------
\version "2.11.17"

<<
        \new Staff {\[b2 b\]   | \[b b\] }
        \new Staff {b2 b       | b4 b b b }
>>
------------------------------------------


I have also two questions about the ligature bracket:

1.
the syntax is \[b b\] instead of b\[ b\], why?, will it change in the future?

2.
In the program reference, the layout object LigatureBracket is said:
"LigatureBracket objects are created by: none"
shouldn't be "Ligature_bracket_engraver" instead of "none"?

thanks