When you install a new forum, the bitfield of the prosilver template is hardcoded to kNg= (1001000011011) in schema_data.sql, while in the documentation it says that the bitfield for prosilver is lNg= (1001010011011).
The prosilver template has lNg= as bitfield in style.cfg, but as a comment.
Also, default bitfield value for installed templates is +Ng= (1111100011011) (at least when they haven't set a bitfield).

I propose to change prosilver bitfield to //g= (1111111111111) (in schema_data.sql and style.cfg) because it has all BBCodes on bbcode.html file and uncomment the bitfield line in style.cfg, because it may be confusing for style autors to have to deal with bitfields.

About the default value for bitfield (when the style.cfg dont have a value for bitfield), i think it should be //g= (1111111111111) or nothing (im not sure about the 0000000000000 bitfield).

Related code:
https://github.com/phpbb/phpbb/blob/master/phpBB/styles/prosilver/style.cfg#L28
https://github.com/phpbb/phpbb/blob/master/phpBB/install/schemas/schema_data.sql#L479
https://github.com/phpbb/phpbb/blob/master/phpBB/includes/acp/acp_styles.php#L1349-L1370

Related issues:
https://tracker.phpbb.com/browse/PHPBB3-3831