Since "newer versions of Excel", there is a new "threaded comments" feature.
It's also simply known as "comments" while the old comments are now known as "notes".
When viewing a comment saved by a recent version of Excel in LibreOffice, we see a message "[Threaded comment] This threaded comment can be viewed, but not edited(...)"
By the way, this kind of feature could be added to a future version of OpenDocument, if not already planned in OpenDocument 1.3.
Created attachment 153704 [details]
Example file for the feature from Excel 365
This feature extends the OOXML standard with a threadedComments subdirectory in xl/, then a threadedComment1.xml file contains the actual comment thread.
Also Excel saves a VML (old style note) formatted version of this comment thread along a warning.
Setting as a new enhancement, since we don't have a similar feature yet in the first place.
Created attachment 153707 [details]
Screenshot of the example file in Excel and Calc 6.3 side by side
Retitling for clarity & searchability.
According to my observations, any such xlsx file opened by LibreOffice, when re-saved to xlsx format, will destroy those comments' metadata (essentially converting them to notes objects) even if you don't touch those comments specifically, not only if "modifying the comment" like the comment says.
Curiosity question: beyond OOXML and the need for a UI for this in LibreOffice Calc, does OpenDocument support threaded comments with replies and usernames etc. in the .ods spreadsheet format?