Comments not being saved in OpenDocumentText-Files

I wanted to comment a colleagues document. This document was uploaded as *.odt-Document.

Like in the example-picture I added a comment. Unfortunately after closing the document it’s gone.

With a *.docx document, comments will be saved

Browser version: All Browsers

Hello @hoc
I believe this is expected result since the ONLYOFFICE native format is OOXML. We recommend converting files to docx/pptx/xlsx formats before the editing process to avoid possible issues: ONLYOFFICE Api Documentation - Opening File
The document editing service downloads the document file from the document storage service using the ID and link provided. At this step the conversion of the file into Office Open XML format is also performed for the document editor better performance and formats compatibility.