BUG: mk_logwatch ab 2.1.0p10 auf Windows komplett funktionsunfähig

Correct. \x0A had been chosen as a safe option: on Windows, some app also do not follow Windows convention and use only \x0A.
Content of file:

ERROR: error 1\x0A 
ERROR:

The line 1 will be reported
The line 2 never. This is because logwatch wait for end of logging operation, i.e. \x0A