Currently the definition of an unquoted-text is as follows:

unquoted-text        ::= ([^{] | '\{')+;

source: https://github.com/projectfluent/syntax/blob/master/fluent.ebnf#L28

For most cases this is fine, however when just relying on this definition it breaks in following example:

opened-new-window = { brandName[gender] ->
 *[masculine] { brandName } otworzyl nowe okno.
  [feminine] { brandName } otworzyla nowe okno. }

In the example given above, it will read the entire line, including the '}' character, which is actually the closing bracket of the root placeable. This problem is fixed if you define an unquoted-text as follows:

unquoted-text        ::= ([^{}] | '\{' | '\}')+;