Earlier quoted context omitted.
The binary logs are append only. The bug tracker entry says that they got "some corrupted logs" but not how. People get corrupted or truncated text logs all the time, they just ignore it because "oh the log ends midway through a line? eh". The ridiculous "oh my god my logs will be always ruined thing" is a beat up by those who need to assassinate something about systemd, because it's always been devoid of any technic…
A truncated text log can still be informative, and I've never had a corrupted text log hang or crash my text editor.
Things which have caused editors to hang or crash: 1. Binary data outside of the US-ASCII visible range 2. Malformed or creative Unicode combinations 3. Very long lines 4. Very many lines 5. Inconsistent line termination 6. Lines with patterns which trigger syntax highlighting, URL underlining, etc. 7. Embedded terminal escape sequences
It's not unreasonable to imagine that the journald developers might spend the same amount of time on safeguards, something which is easier with a well-defined binary format.