Broken chapters from high-precision OGM chapters

I've been looking for a simple text-based chapter file format and found out that MKVToolNix only supports the OGM format (simple chapter format). I couldn't find any specification for it but the format is very straight forward.

As it turns out you're only allowed to specify a precision of 1/1000th seconds for your timestamps, otherwise MKVToolNix silently fails and creates garbage markers. The correct way to handle this would be to either just ignore any characters after \d{2}:\d{2}:\d{2}\.\d{3} or even better just allow the 9-digit precision the MKV container supports (would be an "unofficial" extension of the OGM format but it's atleast in theory backwards compatible).

I've also noticed that the OGM->XML conversion leaves you with ChapterTimeStart tags only, which I'm sure is intended, but kind of weird because every XML I've come across had explicit ChapterTimeEnd tags.