The cause of the problem is a reported bug in AOO Writer- https://bz.apache.org/ooo/show_bug.cgi?id=128356; summary of the bug report is below. See the numbered points at the end for ways to work around the problem. It would seem that asking your editor to observe point 4 might be the simplest solution for the future.
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When Track Changes is enabled and an Annotation is attached to a text range, the file can often be corrupted on reopening. This manifests as two Annotation reference numbers attaching to paragraph format P1, which OpenOffice reports as a "Read Error: Format error discovered ... at n,nnnn (row,col)". Removal of one or other of these Annotation reference numbers will permit the file to open correctly.
We can now replicate the fault reliably where it seems to happen if "text containing two comments attached to a range of characters" is deleted. You can see it happen with comments.odt which I have created for raising a bug report.
Open comments.odt
Set Edit > Changes > Record if not already set
Highlight sentences one and two.
Press delete.
Save.
Open comments.odt
Expected behaviour: File opens correctly
Actual behaviour: File does not open and gives "Format error discovered in the file in sub-document content.xml at 2,2778.
Examination of content.xml shows the first paragraph style definition (P1) has been corrupted by the addition of office:name="__Annotation__2_10671659881" office:name="__Annotation__3_10671659881" Notes
1. You must set Edit > Record > Changes. If it is not set, the error does not occur.
2. Deleting only one sentence does not cause the error.
3. Deleting each comment by the Delete comment command within the comment does not cause the problem. Note that the range of characters is no longer highlighted after the comment has been deleted.
4. If the comments are at a location in the text, and not attached to a range of characters, the error does not occur.
| Edit: Attachment removed by request of owner |