If a format change of a portion of text is tracked, then LibreOffice writes the attribute loext:style-name in the <text:format-change> element. This attribute is missing in https://wiki.documentfoundation.org/Development/ODF_Implementer_Notes/List_of_LibreOffice_ODF_Extensions The list should have been extended by the developer, who introduced this attribute.
I'll look at this.