Set up a spreadsheet with a column formatted as dates - I use dd/mm/yyyy - and enter some dates.

Click and copy a date.

Go to a cell on some other column, create a comment, add the date & some other text.

Show the comment.

Add another comment on a different cell.

Go back and copy another date.  Try to enter it into the original comment.  All sorts of strange things happen.  If the comment isn't in test entry mode clicking on it to set the text cursor is likely to insert the date into another cell.  If the text cursor is set in the comment it can be impossible to set focus on a date cell to copy it.  Eventually the whole selection mechanism can freeze although if there are multiple sheets it can still be possible to move to another sheet but not to select a cell.  At this point the only way to gain access to the data is to close the application and re-open.  On a quick check this seems to affect current OO as well so it seems to be inherited.