In general, you can put a \ at the end of your long command/line to break it to several lines. The sudoers syntax allows this too, that's OK. But: If there is an ex.: space after the \ character, a command/script would break, but sudo doesn't. Question: Is it official (and where is it documented) that sudo accepts spaces after \ on all UNIX-like systems? Example for commands: Normal backslashing: $ echo a; \> echo babA space was put after backslash: $ echo a; \ abash:  : command not found$ 
Does sudo documentedly handles characters after backslash on all UNIX-like systems? - for breaking long lines
sudo
The behavior depends on context because the \ is handled by different applications.The sudoers file is a configuration file from sudo and therefore handled by a parser in sudo. So it depends on the implementation of sudo, which may vary from system to system. E.g. from man sudoers on OSX:Long lines can be continued with a backslash ('\') as the last  character on the line.The other behavior you describe is handled by bash and documented in man bash:If a \<newline> pair  appears,  and  the  backslash  is  not  itself         quoted,  the  \<newline>  is  treated  as a line continuation (that is, it is removed from the input stream and         effectively ignored).Other shells may have different implementations.